256 Meg dynamic random access memory

ABSTRACT

A 256 Meg dynamic random access memory is comprised of a plurality of cells organized into individual arrays, with the arrays being organized into 32 Meg array blocks, which are organized into 64 Meg quadrants. Sense amplifiers are positioned between adjacent rows in the individual arrays while row decoders are positioned between adjacent columns in the individual arrays. In certain of the gap cells, multiplexers are provided to transfer signals from I/O lines to data lines. A datapath is provided which, in addition to the foregoing, includes array I/O blocks, responsive to the datalines from each quadrant to output data to a data read mux, data buffers, and data driver pads. The write data path includes a data in buffer and data write muxes for providing data to the array I/O blocks. A power bus is provided which minimizes routing of externally supplied voltages, completely rings each of the array blocks, and provides gridded power distribution within each of the array blocks. A plurality of voltage supplies provide the voltages needed in the array and in the peripheral circuits. The power supplies are organized to match their power output to the power demand and to maintain a desired ratio of power production capability and decoupling capacitance. A powerup sequence circuit is provided to control the powerup of the chip. Redundant rows and columns are provided as is the circuitry necessary to logically replace defective rows and columns with operational rows and columns. Circuitry is also provided on chip to support various types of test modes.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is directed to integrated circuit memorydesign and, more particularly, to dynamic random access memory (DRAM)designs.

[0003] 2. Description of the Background

[0004] 1. Introduction

[0005] Random access memories (RAMs) are used in a large number ofelectronic devices from computers to toys. Perhaps the most demandingapplications for such devices are computer applications in which highdensity memory devices are required to operate at high speeds and lowpower. To meet the needs of varying applications, two basic types of RAMhave been developed. The dynamic random access memory (DRAM) is, in itssimplest form, a capacitor in combination with a transistor which actsas a switch. The combination is connected across a digitline and apredetermined voltage with a wordline used to control the state of thetransistor. The digitline is used to write information to the capacitoror read information from the capacitor when the signal on the wordlinerenders the transistor conductive.

[0006] In contrast, a static random access memory (SRAM) is comprised ofa more complicated circuit which may include a latch. The SRAMarchitecture also uses digitlines for carrying information to andreading information from each individual memory cell and wordlines tocarry control signals.

[0007] There are a number of design tradeoffs between DRAM and SRAMdevices. Dynamic devices must be periodically refreshed or the datastored will be lost. SRAM devices tend to have faster access times thansimilarly sized DRAM devices. SRAM devices tend to be more expensivethan DRAM devices because the simplicity of the DRAM architecture allowsfor a much higher density memory to be constructed. For those reasons,SRAM devices tend to be used as cache memory whereas DRAM devices tendto be used to provide the bulk of the memory requirements. As a result,there is tremendous pressure on producers of DRAM devices to producehigher density devices in a cost effective manner.

[0008] 2. DRAM Architecture

[0009] A DRAM chip is a sophisticated device which may be thought of asbeing comprised of two portions: the array, which is comprised of aplurality of individual memory cells for storing data, and theperipheral devices, which are all of the circuits needed to readinformation into and out of the array and support the other functions ofthe chip. The peripheral devices may be further divided into data pathelements, address path elements, and all other circuits such as voltageregulators, voltage pumps, redundancy circuits, test logic, etc.

[0010] A. The Array

[0011] Turning first to the array, the topology of a modern DRAM array 1is illustrated in FIG. 1. The array 1 is comprised of a plurality ofcells 2 with each cell constructed in a similar manner. Each cell iscomprised of a rectangular active area, which in FIG. 1 is a N+ activearea. A dotted box 3 illustrates where one transistor/capacitor pair isfabricated while a dotted box 4 illustrates where a secondtransistor/capacitor pair is fabricated. A wordline WL1 runs throughdotted box 3, and at least a portion of where that wordline overlays theN+ active area is where the gate of the transistor is formed. To theleft of the wordline WL1 in dotted box 3, one terminal of the transistoris connected to a storage node 5 which forms the capacitor. The otherterminal of the capacitor is connected to a cell plate. To the right ofthe wordline WL1, the other terminal of the transistor is connected to adigitline D2 at a digitline contact 6. The transistor/capacitor pair indotted box 4 is a mirror image of the transistor/capacitor pair indotted box 3. The transistor within dotted box 4 is connected to its ownwordline WL2 while sharing the digitline contact 6 with the transistorin the dotted box 3.

[0012] The wordlines WL1 and WL2 may be constructed of polysilicon whilethe digitline may be constructed of polysilicon or metal. The capacitorsmay be formed with an oxide-nitride-oxide-dielectric between twopolysilicon layers. In some processes, the wordline polysilicon issilicided to reduce the resistance which permits longer wordlinesegments without impacting speed.

[0013] The digitline pitch, which is the width of the digitline plus thespace between digitlines, dictates the active area pitch and thecapacitor pitch. Process engineers adjust the active area width and theresulting field oxide width to maximize transistor drive and minimizetransistor-to-transistor leakage. In a similar manner, the wordlinepitch dictates the space available for the digitline contact, transistorlength, active area length, field poly width, and capacitor length. Eachof those features is closely balanced by process engineers to maximizecapacitance and yield and to minimize leakage.

[0014] B. The Data Path Elements

[0015] The data path is divided into the data read path and the datawrite path. The first element of the data read path, and the lastelement of the data write path, is the sense amplifier. The senseamplifier is actually a collection of circuits that pitch up to thedigitlines of a DRAM array. That is, the physical layout of each circuitwithin the sense amplifier is constrained by the digitline pitch. Forexample, the sense amplifiers for a specific digitline pair aregenerally laid out within the space of four digitlines. One senseamplifier for every four digitlines is commonly referred to as quarterpitch or four pitch.

[0016] The circuits typically comprising the sense amplifier includeisolation transistors, circuits for digitline equilibration and bias,one or more N-sense amplifiers, one or more P-sense amplifiers, and I/Otransistors for connecting the digitlines to the I/O signal lines. Eachof those circuits will be discussed.

[0017] Isolation transistors provide two functions. First, if the senseamplifiers are positioned between and connected to two arrays, theyelectrically isolate one of the two arrays. Second, the isolationtransistors provide resistance between the sense amplifier and thehighly capacitive digitlines, thereby stabilizing the sense amplifierand speeding up the sensing operation. The isolation transistors areresponsive to a signal produced by an isolation driver. The isolationdriver drives the isolation signal to the supply potential and thendrives the signal to a pumped potential which is equal to the value ofthe charge on the digit lines plus the threshold voltage of theisolation transistors.

[0018] The purpose of the equilibration and bias circuits is to ensurethat the digitlines are at the proper voltages to enable a readoperation to be performed. The N-sense amplifiers and P-sense amplifierswork together to detect the signal voltage appearing on the digitlinesin a read operation and to locally drive the digitlines in a writeoperation. Finally, the I/O transistors allow data to be transferredbetween digitlines and I/O signal lines.

[0019] After data is read from an mbit and latched by the senseamplifier, it propagates through the I/O transistors onto the I/O signallines and into a DC sense amplifier. The I/O lines are equilibrated andbiased to a voltage approaching the peripheral voltage Vcc. The DC senseamplifier is sometimes referred to as the data amplifier or readamplifier. The DC sense amplifier is a high speed, high gain,differential amplifier for amplifying very small read signals appearingon the I/O lines into full CMOS data signals input to an output databuffer. In most designs, the array sense amplifiers have very limiteddrive capability and are unable to drive the I/O lines quickly. Becausethe DC sense amplifier has a very high gain, it amplifies even theslightest separation in the I/O lines into full CMOS levels.

[0020] The read data path proceeds from the DC sense amplifier to theoutput buffers either directly or through data read multiplexers(muxes). Data read muxes are commonly used to accommodate multiple partconfigurations with a single design. For an ×16 part, each output bufferhas access to only one data read line pair. For an ×8 part, the eightoutput buffers each have two pairs of data lines available therebydoubling the quantity of mbits accessible by each output. Similarly, fora ×4 part, the four output buffers have four pairs of datalinesavailable, again doubling the quantity of mbits available for eachoutput.

[0021] The final element in the read data path is the output buffercircuit. The output buffer circuit consists of an output latch and anoutput driver circuit. The output driver circuit typically uses aplurality of transistors to drive an output pad to a predeterminedvoltage, Vccx or ground, typically indicating a logic level 1 or logiclevel 0, respectively.

[0022] A typical DRAM data path is bidirectional, allowing data to beboth read from and written to the array. Some circuits, however, aretruly bidirectional, operating the same regardless of the direction ofthe data. An example of such bidirectional circuits is the senseamplifiers. Most of the circuits, however, are unidirectional, operatingon data in only a read operation or a write operation. The DC senseamplifiers, data read muxes, and output buffer circuits are examples ofunidirectional circuits. Therefore, to support data flow in bothdirections, unidirectional circuits must be provided in complementarypairs, one for reading and one for writing. The complementary circuitsprovided in the data write path are the data input buffers, data writemuxes, and write driver circuits.

[0023] The data input buffers consist of both nMOS and pMOS transistors,basically forming a pair of cascaded inverters. Data write muxes, likedata read muxes, are often used to extend the versatility of a design.While some DRAM designs connect the input buffer directly to the writedriver circuits, most architectures place a block of data write muxesbetween the input buffers and the write drivers. The muxes allow a givenDRAM design to support multiple configurations, such as ×4, ×8, and ×16parts. For ×16 operation, each input buffer is muxed to only one set ofdata write lines. For ×8 operation, each input buffer is muxed to twosets of data write lines, doubling the quantity of mbits available toeach input buffer. For ×4 operation, each input buffer is muxed to foursets of data writelines, again doubling the number of mbits available tothe remaining four operable input buffers. As the quantity of inputbuffers is reduced, the amount of column address space is increased forthe remaining buffers.

[0024] A given write driver is generally connected to only one set ofI/O lines, unless multiple sets of I/O lines are fed by a single writedriver via additional muxes. The write driver uses a tri-state outputstage to connect to the I/O lines. Tri-state outputs are necessarybecause the I/O lines are used for both read and write operations. Thewrite driver remains in a high impedance state unless the signal labeled“write” is high, indicating a write operation. The drive transistors aresized large enough to insure a quick, efficient, write operation.

[0025] The remaining element of the data write path is, as mentioned,the bidirectional sense amplifier which is connected directly to thearray.

[0026] C. The Address Path Elements

[0027] Up to this point we have been discussing data paths. The movementof data into or out of a particular location within the array isperformed under the control of address information. We next turn to adiscussion of the address path elements.

[0028] Since the 4 Kb generation of DRAMs, DRAMs have used multiplexedaddresses. Multiplexing in DRAMs is possible because DRAM operation issequential. That is, column operations follow row operations. Thus, thecolumn address is not needed until the sense amplifiers for anidentified row have latched, and that does not occur until sometimeafter the wordline has fired. DRAMs operate at higher current levelswith multiplexed addressing, because an entire page (row address) isopened with each row access. That disadvantage is overcome by the lowerpackaging costs associated with multiplexed addresses. Additionally,because of the presence of the column address strobe signal (CAS*),column operation is independent of row operation, enabling a page toremain open for multiple, high-speed, column accesses. That page modetype of operation improves system performance because column access timeis much shorter than row access time. Page mode operation appears inmore advanced forms, such as extended data out (EDO) and burst EDO(BEDO), providing even better system performance through a reduction ineffective column access time.

[0029] The address path for a DRAM can be broken into two parts: the rowaddress path and the column address path. The design of each path isdictated by a unique set of requirements. The address path, unlike thedata path, is unidirectional. That is, address information flows onlyinto the DRAM. The address path must achieve a high level of performancewith minimal power and die area, just like every other aspect of DRAMdesign. Both paths are designed to minimize propagation delay andmaximize DRAM performance.

[0030] The row address path encompasses all of the circuits from theaddress input pad to the wordline driver. Those circuits generallyinclude the row address input buffers, CAS before RAS counter (CBRcounter), predecode logic, array buffers, redundancy logic (treatedseparately hereinbelow), row decoders, and phase drivers.

[0031] The row address buffer consists of a standard input buffer andthe additional circuits necessary to implement functions required forthe row address path. The CBR counter consists of a single inverter anda pair of inverter latches coupled to a pair of complementary muxes toform a one bit counter. All of the CBR counters from each row addressbuffer are cascaded together to form a CBR ripple counter. By cyclingthrough all possible row address combinations in a minimum of clockpulses, the CBR ripple counter provides a simple means of internallygenerating refresh addresses.

[0032] There are many types of predecode logic used for the row addresspath. Predecoded address lines may be formed by logically combining(AND) addresses as shown in Table 1. TABLE 1 Predecoded address truthtable PRO1 PRO1 RA<0> RA<1> PRO1 (n) <0> PRO1<1> <2> PRO1<3> 0 0 0 1 0 00 1 0 1 0 1 0 0 0 1 2 0 0 1 0 1 1 3 0 0 0 1

[0033] The remaining addresses are identically coded except for RA<12>,which is essentially a “don't care”. Advantages to predecoded addressesinclude lower power due to fewer signals making transitions duringaddress changes and higher efficiency because of the reduced number oftransistors necessary to decode addresses. Predecoding is especiallybeneficial in redundancy circuits. Predecoded addresses are usedthroughout most DRAM designs today.

[0034] Array buffers drive the predecoded address signals into the rowdecoders. In general, the buffers are no more than cascaded inverters,but in some cases they may include static logic gates or leveltranslators, depending upon the row decoder requirements.

[0035] Row decoders must pitch up to the mbit arrays. There are avariety of implementations, but however implemented, the row decoderessentially consists of two elements: a wordline driver and an addressdecoder tree. With respect to the wordline driver, there are three basicconfigurations: the NOR driver, the inverter (CMOS) driver, and thebootstrap driver. Just about any type of logic may be used for theaddress decoder tree. Static logic, dynamic logic such as precharge andevaluate logic, pass gate logic, or some combination thereof may beprovided to decode the predecoded address signals. Additionally, thedrivers and associated decode trees can be configured either as localrow decodes for each array section or as global row decodes that drive amultitude of array sections.

[0036] The wordline driver in the row decoder causes the wordline tofire in response to a signal called PHASE. Essentially, the PHASE signalis the final address term to arrive at the wordline driver. Its timingis carefully determined by the control logic. PHASE cannot fire untilthe row addresses are set up in the decode tree. Normally, the timing ofPHASE also includes enough time for the row redundancy circuits toevaluate the current address. The phase driver can be composed ofstandard static logic gates.

[0037] The column address path consists of the input buffers, addresstransition detection (ATD) circuits, predecode logic, redundancy logic(discussed below), and column decoders. The column address input buffersare similar in construction and operation to the row address inputbuffers. The ATD circuit detects any transition that occurs on anaddress pin to which the circuit is dedicated. ATD output signals fromall of the column addresses are routed to an equilibration drivercircuit. The equilibration driver circuit generates a set ofequilibration signals for the DRAM. The first of these signals isEquilibrate I/O (EQIO) which is used in the arrays to forceequilibration of the I/O lines. The second signal generated by theequilibration driver is called Equilibrate Sense Amps (EQSA). Thatsignal is generated from address transitions occurring on all of thecolumn addresses, including the least significant address.

[0038] The column addresses are fed into predecode logic which is verysimilar to the row address predecode logic. The address signalsemanating from the predecode logic are buffered and distributedthroughout the die to feed the column decoders.

[0039] The column decoders represent the final elements that must pitchup to the array mbits. Unlike row decoder implementation, though, columndecoder implementation is simple and straightforward. Static logic gatesmay be used for both the decode tree elements and the driver output.Static logic is used primarily because of the nature of columnaddressing. Unlike row addressing, which occurs once per RAS* cycle witha modest precharge period until the next cycle, column addressing canoccur multiple times per RAS* cycle. Each column is held open until asubsequent column appears. In a typical implementation, the address treeconsists of combinations of NAND or NOR gates. The column decoder outputdriver is a simple CMOS inverter.

[0040] The row and column addressing scheme impacts the refresh rate forthe DRAM. Normally, when refresh rates change for a DRAM, a higher orderaddress is treated as a “don't care” address, thereby decreasing the rowaddress space, but increasing the column address space. For example, a16 Mb DRAM bonded as a 4 Mb ×4 part could be configured in severalrefresh rates: 1K, 2K, and 4K. Table 1 below shows how row and columnaddressing is related to those refresh rates for the 16 Mb example. Inthis example, the 2K refresh rate would be more popular because it hasan equal number of row and column addresses, sometimes referred to assquare addressing. TABLE 2 Refresh rate versus row and column addressesRefresh Row Column Rate Rows Columns Addresses Addresses 4K 4096 1024 1210 2K 2048 2048 11 11 1K 1024 4096 10 12

[0041] D. Other Circuits

[0042] Additional circuits are provided to enable various otherfeatures. For example, circuits to enable test modes are typicallyincluded in DRAM designs to extend test capabilities, speed componenttesting, or subject a part to conditions that are not seen during normaloperation. Two examples are address compression and data compressionwhich are two special test modes usually supported by the design of thedata path. Compression test modes yield shorter test times by allowingdata from multiple array locations to be tested and compressed on-chip,thereby reducing the effective memory size. The costs of any additionalcircuitry to implement test modes must be balanced against cost benefitsderived from reductions in test time. It is also important thatoperation in test mode achieve 100% correlation to operation of non-testmode. Correlation is often difficult to achieve, however, becauseadditional circuitry must be activated during compression, modifying thenoise and power characteristics on the die.

[0043] Additional circuitry is added to the DRAM to provide redundancy.Redundancy has been used in DRAM designs since the 256 Kb generation toimprove yield. Redundancy involves the creation of spare rows andcolumns which can be used as a substitute for normal rows and columns,respectively, which are found to be defective. Additional circuitry isprovided to control the physical encoding which enables the substitutionof a usable device for a defective device. The importance of redundancyhas continued to increase as memory density and size have increased.

[0044] The concept of row redundancy involves replacing bad wordlineswith good wordlines. The row to be repaired is not physically replaced,but rather it is logically replaced. In essence, whenever a row addressis strobed into a DRAM by RAS*, the address is compared to the addressesof known bad rows. If the address comparison produces a match, then areplacement wordline is fired in place of the normal (bad) wordline. Thereplacement wordline can reside anywhere on the DRAM. Its location isnot restricted to the array that contains the normal wordline, althougharchitectural considerations may restrict its range. In general, theredundancy is considered local if the redundant wordline and normalwordline must always be on the same subarray.

[0045] Column redundancy is a second type of repair available in mostDRAM designs. Recall that column accesses can occur multiple times perRAS* cycle. Each column is held open until a subsequent column appears.Because of that, circuits that are very different from those seen in therow redundancy are used to implement column redundancy.

[0046] The DRAM circuit also carries a number of circuits for providingthe various voltages used throughout the circuit.

[0047] 3. Design Considerations

[0048] U.S. patent application Ser. No. 08/460,234, entitled SingleDeposition Layer Metal Dynamic Random Access Memory, filed Aug. 17, 1995and assigned to the same assignee as the present invention is directedto a 16 Meg DRAM. U.S. patent application Ser. No. 08/420,943, entitledDynamic Random Access Memory, filed Jun. 4, 1995 and assigned to thesame assignee as the present invention is directed to a 64 Meg DRAM. Aswill be seen from a comparison of the two aforementioned patentapplications, it is not a simple matter to quadruple the size of a DRAM.Quadrupling the size of a 64 Meg DRAM to a 256 Meg DRAM poses asubstantial number of problems for the design engineer. For example, tostandardize the part so that 256 Meg DRAMs from different manufacturerscan be interchanged, a standard pin configuration has been established.The location of the pins places constraints on the design engineer withrespect to where circuits may be laid out on the die. Thus, the entirelayout of the chip must be reengineered so as to minimize wire runs,eliminate hot spots, simplify the architecture, etc.

[0049] Another problem faced by the design engineer in designing a 256Meg DRAM is the design of the array itself. Using prior art arrayarchitectures does not provide sufficient space for all of thecomponents which must pitch up to the array.

[0050] Another problem involves the design of the data path. The datapath between the cells and the output pads must be as short as possibleso as to minimize line lengths to speed up part operation while at thesame time present a design which can be manufactured using existingprocesses and machines.

[0051] Another problem faced by the design engineer involves the issueof redundancy. A 256 Meg DRAM requires the fabrication of millions ofindividual devices, and millions of contacts and vias to enable thosedevices to be interconnected. With such a large number of components andinterconnections, even a very small failure rate results in a certainnumber of defects per die. Accordingly, it is necessary to designredundancy schemes to compensate for such failures. However, withoutpractical experience in manufacturing the part and learning whatfailures are likely to occur, it is difficult to predict the type andamount of redundancy which must be provided.

[0052] Another problem involves latch-up in the isolation driver circuitwhen the pumped potential is driven to ground. Latch-up occurs whenparasitic components give rise to the establishment of low-resistancepaths between the supply potential and ground. A large amount of currentflows along the low-resistance paths and device failure may result.

[0053] Designing the on-chip test capability also presents problems.Test modes, as opposed to normal operating modest are used to testmemory integrated circuits. Because of the limited number of pinsavailable and the large number of components which must be tested,without some type of test compression architecture, the time which eachDRAM would have to spend in a test fixture would be so long as to becommercially unreasonable. It is known to use test modes to reduce theamount of time required to test the memory integrated circuit, as wellas to ensure that the memory integrated circuit meets or exceedsperformance requirements. Putting a memory integrated circuit into atest mode is described in U.S. Pat. No. 5,155,704, entitled “MemoryIntegrated Circuit Test mode Switching” to Walther et al. However,because the test mode operates internal to the memory, it is difficultto determine whether the memory integrated circuit successfullycompleted one or more test modes. Therefore, a need exists for providinga solution to verify successful or unsuccessful execution of a testmode. Furthermore, it would be desirable that such a solution haveminimal impact with respect to additional circuitry. Certain test modes,such as the all row high test mode, must be rethought with respect to apart as large as a 256 Meg chip because the current required for such atest would destroy power transistors servicing the array.

[0054] Providing power for a chip as large as a 256 Meg DRAM alsopresents its own set of unique problems. Refresh rates may cause thepower needed to vary greatly. Providing voltage pumps and generators ofsufficient size to provide the necessary power may result in noise andother undesirable side effects when maximum power is not required.Additionally, reconfiguring the DRAM to achieve a usable part in theevent of component failure may result in voltage pumps and generatorsill sized for the smaller part.

[0055] Even something as basic as powering up the device must berethought in the context of such a large and complicated device as a 256Meg DRAM. Prior art timing circuits use an RC circuit to wait apredetermined period of time and then blindly bring up the variousvoltage pumps and generators. Such systems do not receive feedback and,therefore, are not responsive to problems during power up. Also, to workreliably, such systems are conservative in the event some voltage pumpsor generators operated more slowly than others. As a result, in mostcases, the power up sequence was more time consuming than it needed tobe. In a device as complicated as a 256 Meg DRAM, it is necessary toensure that the device powers up in a manner that permits the device tobe properly operated in a minimum amount of time.

[0056] All of the foregoing problems are superimposed upon the problemswhich every memory design engineer faces such as satisfying theparameters set for the memory, e.g., access time, power consumption,etc., while at the same time laying out each and every one of millionsof components and interconnections in a manner so as to maximize yieldand minimize defects. Thus, the need exists for a 256 Meg DRAM whichovercomes the foregoing problems.

SUMMARY OF THE INVENTION

[0057] The present invention is directed to a 256 Meg DRAM, althoughthose of ordinary skill in the art will recognize that the circuits andarchitecture disclosed herein may be used in memory devices of othersizes or even other types of circuits.

[0058] The present invention is directed to a memory device comprised ofa triple polysilicon, double metal main array of 256 Meg. The main arrayis divided into four array quadrants each of 64 Meg. Each of the arrayquadrants is broken up into two 32 Meg array blocks. Thus, there areeight 32 Meg array blocks in total. Each of the 32 Meg array blocksconsists of 128 256 k bit subarrays. Thus, there are 1,024 256 k bitsubarrays in total. Each 32 Meg array block features sense amp stripswith single p-sense amps and boosted wordline voltage Vccp isolationtransistors. Local row decode drivers are used for wordline driving andto provide “streets” for dataline routing to the circuits outside of thearray. The I/O lines which route through the sense amps extend acrosstwo subarray blocks. That permits a 50% reduction in the number of datamuxes required in the gap cells. The data muxes are carefully programmedto support the firing of two rows per 32 Meg block without datacontention on the data lines. Additionally, the architecture of thepresent invention routes the redundant wordline enable signal though thesense amp in metal two to ensure quick deselect of the normal row. Thenormal phase lines are rematched to appropriate redundant wordlinedrivers for efficient reuse of signals.

[0059] Also, the data paths for reading information into and writinginformation out of the array have been designed to minimize the lengthof the data path and increase overall operational speed. In particular,the output buffers in the read data path include a self-timed path toensure that the holding transistor connected between the boosted voltageVccp and a boot capacitor is turned off before the boot capacitor isunbooted. That modification ensures that charge is not removed from theVccp source when turning off a logic “1” level.

[0060] The power busing scheme of the present invention is based uponcentral distribution of voltages from the pads area. On-chip voltagesupplies are distributed throughout the center pads area for generationof both peripheral power and array power. The array voltage is generatedin the center of the design for distribution to the arrays from acentral web. Bias and boosted voltages are generated on either side ofthe regulator producing the array voltage for distribution throughoutthe tier logic. The web surrounds each 32 Meg array block for efficient,low-resistant distribution. The 32 Meg arrays feature fully griddedpower distribution for better IR and electromigration performance.

[0061] Redundancy schemes have been built into the design of the presentinvention to enable global as well as local repair.

[0062] The present invention includes a method and apparatus forproviding contemporaneously generated (status) information or programmedinformation. In particular, address information may be used as a testkey. A detect circuit, in electrical communication with decodingcircuits, receives an enable signal which activates the detection of anon-standard or access voltage. By non-standard or access voltage it ismeant that a voltage outside of the logic level range (e.g.,transistor-transistor logic) is used for test logic. The decodingcircuit uses the address information as a vector to access a selectedtype or types of information. With such a vector, a bank, havinginformation stored therein, may be selected from a plurality of banks,and a bit or bits within the selected bank may be accessed. Depending onthe test mode selected, either programmed information or statusinformation will be accessed. The decoding circuits and the detectcircuit are in electrical communication with a select circuit forselecting between test mode operation and standard memory operation(e.g., a memory read operation).

[0063] The power and voltage requirements of a 256 Meg DRAM prevententering the all row high test in the manner used in other, smallerDRAMs. To reduce the current requirements, in the present invention onlysubsets of the rows are brought high at a time. The timing of thosesubsets of rows is handled by cycling CAS. The CAS before RAS (CBR)counter, or another counter, may be used to determine which subset ofrows is brought high on each CAS cycle. Various test compressionfeatures are also designed into the architecture.

[0064] The present invention also includes a powerup sequence circuit toensure that a powerup sequence occurs in the right order. Inputs to thesequence circuit are the current levels of the voltage pumps, thevoltage generator, the voltage regulator, and other circuitry importantto correctly powerup the part. The logic to control the sequence circuitmay be constructed using analog circuitry and level detectors to ensurea predictable response at low voltages. The circuitry may also handlepower glitches both during and after initial powerup.

[0065] The 32 Meg array blocks comprising the main array can each beshut down if the quantity of failures or the extent of the failuresexceed the array block's repair capability. That shutdown is bothlogical and physical. The physical shutdown includes removing power suchas the peripheral voltage Vcc, the digitline bias voltage DVC2, and thewordline bias voltage Vccp. The switches which disconnect power from theblock must, in some designs, be placed ahead of the decouplingcapacitors for that block. Therefore, the total amount of decouplingcapacitance available on the die is reduced with each array block thatis disabled. Because the voltage regulator's stability can in large partbe dependant upon the amount of decoupling capacitance available, it isimportant that as 32 Meg array blocks are disabled, a correspondingvoltage regulator section be similarly disabled. The voltage regulatorof the present invention has a total of twelve power amplifiers. Foreight of the twelve, one of the eight is associated with one of theeight array blocks. The four remaining power amplifiers are associatedwith decoupling capacitors not effected by the array switches.Furthermore, because the total load current is reduced with each 32 Megarray block that is disconnected, the need for the additional poweramplifiers is also reduced.

[0066] The present invention also incorporates address remapping toensure contiguous address space for the partial die. That designrealizes a partial array by reducing the address space rather thaneliminating DQs.

[0067] The present invention also includes a unique on-chip voltageregulator. The power amplifiers of the voltage regulator have a closedloop gain of 1.5. Each amplifier has a boost circuit which increases theamplifier's slew rate by increasing the differential pair bias current.The design includes additional amplifiers that are specialized tooperate when the pumps fire and a very low Icc standby amplifier. Thedesign allows for multiple refresh operations by enabling additionalamplifiers as needed.

[0068] The present invention also includes a tri-region voltagereference which utilizes a current related to the externally suppliedvoltage Vccx in conjunction with an adjustable (trimmable) pseudo diodestack to generate a stable low voltage reference.

[0069] The present invention also includes a unique design of a Vccpvoltage pump which is configurable for various refresh options. The 256Meg chip requires 6.5 mA of Iccp current in the 8 k refresh mode andover 12.8 mA in the 4 k refresh mode. That much variation in loadcurrent is best managed by bringing more pump sections into operationfor the 4 k refresh mode. Accordingly, the design of the Vccp voltagepump of the present invention uses three pump circuits for 8 k and sixpump circuits for 4 k refresh mode. The use of six pump circuits for the8 k mode is unacceptable from a noise standpoint and actually producesexcessive Vccp ripple when the pumps are so lightly loaded.

[0070] The present invention also includes a unique DVC2cellplate/digitline bias generator with an output status sensor. Thepowerup sequence circuit previously described requires that each powersupply be monitored as to its status when powering up. The DVC2generator constructed according to the teachings of the presentinvention allows its status to be determined through the use of bothvoltage and current sensing. The voltage sensing is a window detectorwhich determines if the output voltage is one Vt above ground Vss andone Vt below the array voltage Vcca. The current sensing is based uponmeasuring changes in the output current as a function of time. If theoutput current reaches a stable steady state level, the current sensorindicates a steady state condition. Additionally, a DC current monitoris present which determines if the steady state current exceeds a presetthreshold. The output of the DC current monitor can either be used inthe powerup sequence or to identify row to column or cellplate todigitline shorts in the arrays. Following completion of the powerupsequence, the sensor output status is disabled.

[0071] The present invention also includes devices to support partialarray power down of the isolation driver circuit. The devices ensurethat no current paths are produced when the voltage Vccp, which is usedto control the isolation transistors, is driven to ground and, thus,latch-up is avoided. Also, the devices ensure that all components in theisolation driver that are connected to the voltage Vccp are disabledwhen the driver is disabled.

[0072] The architecture and circuits of the present invention representa substantial advance over the art. For example, the array architecturerepresents an improvement for several reasons. One, the data is routeddirectly to the peripheral circuits which shortens the data path andspeeds part operation. Second, doubling the I/O line length simplifiesgap cell layout and provides the framework for 4 k operation, i.e., tworows of the 32 Meg block. Third, sending the Red signal through thesense amps provides for faster operation, and when combined with PHASEsignal remapping, a more efficient design is achieved.

[0073] The improved output buffer used in the data path of the presentinvention lowers Iccp current when the buffer turns off a logic “1”level.

[0074] The unique power busing layout of the present inventionefficiently uses die size. Central distribution of array power is wellsuited to the 256 Meg DRAM design. Alternatives in which regulators arespread around the die require that the external voltage Vccx be routedextensively around the die. That results in inefficiencies and requiresa larger die.

[0075] Other advantages that flow from the architecture and circuits ofthe present invention include the following. The generation of statusinformation allows us to confirm that the port is still in the desiredtest mode at the end of a test mode cycle and allows us to check everypossible test mode. Combining this with fuse ID information reduces thearea penalty. During the all row high test mode, the timing of the rowscan be controlled better using the CAS cycle. Also, the number of rowsubsets that can be brought high can be greater than four. The powerupsequence circuit provides for more foolproof operation of the DRAM. Thepowerup sequence circuit also handles power glitches both during powerupand during normal operation. The disabling of 32 Meg array blockstogether with their corresponding voltage regulator section, whilemaintaining a proper ratio of output stages to decoupling capacitance,ensures voltage regulator stability despite changes in partconfiguration stemming from partial array implementation The on-chipvoltage regulator provides low standby current, improved operatingcharacteristics over the entire operating range, and better flexibility.The adjustable, tri-region voltage reference produces a voltage in amanner that ensures that the output amplifiers (which have gain) willoperate linearly over the entire voltage range. Furthermore, moving thegain to the output amplifiers improves common mode range and overallvoltage characteristics. Also, the use of pMOS diodes creates thedesired burn-in characteristics. The variable capacity voltage pumpcircuit, in which capacity is brought on line only when needed, keepsoperating current to the level needed depending upon the refresh mode,and also lowers noise level in the 8 k refresh mode. Thecellplate/digitline bias generator allows the determination of the DVC2status in support of the powerup sequence circuit. Those advantages andbenefits of the present invention, and others, will become apparent fromthe Description of the Preferred Embodiments hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] For the present invention to be clearly understood and readilypracticed, the present invention will be described in conjunction withthe following figures wherein:

[0077]FIG. 1 illustrates the topology of one type of array architecturefound in the prior art;

256 Meg DRAM Architecture (See Section II)

[0078]FIG. 2 is a block diagram illustrating a 256 Meg DRAM constructedaccording to the teachings of the present invention;

[0079] FIGS. 3A-3E illustrate one of the four 64 Meg arrays whichcomprise the 256 Meg DRAM found in FIG. 2;

Array Architecture (See Section III)

[0080]FIG. 4 is a block diagram illustrating the 8×16 array ofindividual 256 k arrays which make up one of the 32 Meg array blocks;

[0081]FIG. 5 is a block diagram of one 256 k array with associated senseamps and row decoders;

[0082]FIG. 6A illustrates the details of the 256 k array shown in FIG.5;

[0083]FIG. 6B illustrates the details of one of the row decoders shownin FIG. 5;

[0084]FIG. 6C illustrates the details of one of the sense amps shown inFIG. 5;

[0085]FIG. 6D illustrates the details of one of the array multiplexersand one of the sense amp drivers shown in FIG. 5;

Data and Test Paths (See Section IV)

[0086]FIG. 7 is a diagram illustrating the connections made by the datamultiplexers within one of the 32 Meg array blocks;

[0087]FIG. 8 is a block diagram illustrating the data read path from thearray I/O block to the data pad driver and the data write path from thedata in buffer back to the array I/O blocks;

[0088]FIG. 9 is a block diagram illustrating the array I/o block foundin FIG. 8;

[0089]FIGS. 10A through 10D illustrate the connection details of thearray I/O block shown in FIG. 9;

[0090]FIG. 11 illustrates the details of the data select blocks found inFIG. 9;

[0091]FIGS. 12A and 12B illustrate the details of the data blocks foundin FIG. 9;

[0092]FIGS. 13A and 13B illustrate the details of a dc sense amp controlused in conjunction with the dc sense amps found in the data blocks;

[0093]FIG. 14 illustrates the details of the mux decode A circuit shownin FIG. 13A;

[0094]FIG. 15 illustrates the details of the mux decode B circuit shownin FIG. 13A;

[0095]FIGS. 16A, 16B, and 16C illustrate the details of the data readmux shown in FIG. 8;

[0096]FIG. 17 illustrates the details of the data read mux controlcircuit shown in FIG. 8;

[0097]FIG. 18 illustrates the details of the data output buffer shown inFIG. 8;

[0098]FIG. 19 illustrates the details of the data out control circuitshown in FIG. 8;

[0099]FIG. 20 illustrates the details of the data pad driver shown inFIG. 8;

[0100]FIG. 21 illustrates the details of the data read bus bias circuitshown in FIG. 8;

[0101]FIG. 22 illustrates the details of the data in buffer and data inbuffer enable shown in FIG. 8;

[0102]FIG. 23 illustrates the details of the data write mux shown inFIG. 8;

[0103]FIG. 24 illustrates the details of the data write mux controlshown in FIG. 8;

[0104]FIG. 25 illustrates the details of the data test comp. circuitshown in FIG. 9;

[0105]FIG. 26 illustrates the details of the data test block b shown inFIG. 8;

[0106]FIG. 27 illustrates the data path test block shown in FIGS. 8 and26;

[0107]FIG. 28 illustrates the details of the data test DC 21 circuitsshown in FIG. 27;

[0108]FIG. 29 illustrates the details of the data test blocks shown inFIG. 27;

Product Configuration and Exemplary Design Specifications (See SectionV)

[0109]FIG. 30 illustrates the mapping of the address bits to the 256 Megarray;

[0110]FIGS. 31A, 31B, and 31C are a bonding diagram illustrating the pinassignments for a ×4, ×8, and ×16 part;

[0111]FIG. 32A illustrates a column address map for the 256 Meg memorydevice of the present invention;

[0112]FIG. 32B illustrates a row address map for a 64 Meg quadrant;

Bus Architecture (See Section VI)

[0113]FIGS. 33A, 33B, and 33C are a diagram illustrating the primarypower bus layout;

[0114]FIGS. 33D and E are a diagram illustrating the approximatepositions of the pads, the 32 Meg arrays, and the voltage supplies;

[0115]FIGS. 34A, 34B, and 34C are a diagram illustrating the padsconnected to the power buses;

Voltage Supplies (See Section VII)

[0116]FIG. 35 is block diagram illustrating the voltage regulator whichmay be used to produce the peripheral voltage Vcc and the array voltageVcca;

[0117]FIG. 36A illustrates the details of the tri-region voltagereference circuit shown in FIG. 35;

[0118]FIG. 36B is a graph of the relationship between the peripheralvoltage Vcc and the externally supplied voltage Vccx; FIG. 36Cillustrates the details of the logic circuit 1 shown in FIG. 35;

[0119]FIG. 36D illustrates the details of the Vccx detect circuits shownin FIG. 35;

[0120]FIG. 36E illustrates the details of the logic circuit 2 shown inFIG. 35;

[0121]FIG. 36F illustrates the details of the power amplifiers shown inFIG. 35;

[0122]FIG. 36G illustrates the details of the boost amplifiers shown inFIG. 35;

[0123]FIG. 36H illustrates the details of the standby amplifier shown inFIG. 35;

[0124]FIG. 36I illustrates the details of the power amplifiers in thegroup of twelve power amplifiers illustrated in FIG. 35;

[0125]FIG. 37 is a block diagram illustrating the voltage pump which maybe used to produce a voltage Vbb used as a back bias for the die;

[0126]FIG. 38A illustrates the details of the pump circuits shown inFIG. 37;

[0127]FIG. 38B illustrates the details of the Vbb oscillator circuitshown in FIG. 37;

[0128]FIG. 38C illustrates the details of the Vbb reg select shown inFIG. 37;

[0129]FIG. 38D illustrates the details of the Vbb differential regulator2 circuit shown in FIG. 37;

[0130]FIG. 38E illustrates the details of the Vbb regulator 2 circuitshown in FIG. 37;

[0131]FIG. 39 is a block diagram illustrating the Vcc pump which may beused to produce the boosted voltage Vccp for the wordline drivers;

[0132]FIG. 40A illustrates the details of the Vccp regulator selectcircuit shown in FIG. 39;

[0133]FIG. 40B illustrates the details of the Vccp burnin circuit shownin FIG. 39;

[0134]FIG. 40C illustrates the details of the Vccp pullup circuit shownin FIG. 39;

[0135]FIG. 40D illustrates the details of the Vccp clamps shown in FIG.39;

[0136]FIG. 40E illustrates the details of the Vccp pump circuits shownin FIG. 39;

[0137]FIG. 40F illustrates the details of the Vccp Lim2 circuits shownin FIG. 40E;

[0138]FIG. 40G illustrates the details of the Vccp Lim3 circuits shownin FIG. 40E;

[0139]FIG. 40H illustrates the details of the Vccp oscillator shown inFIG. 39;

[0140]FIG. 40I illustrates the details of the Vccp regulator 3 circuitshown in FIG. 39;

[0141]FIG. 40J illustrates the details of the Vccp differentialregulator circuit shown in FIG. 39;

[0142]FIG. 41 is a block diagram illustrating the DVC2 generator whichmay be used to produce bias voltages for the digitlines (DVC2) and thecellplate (AVC2);

[0143]FIG. 42A illustrates the details of the voltage generator shown inFIG. 41;

[0144]FIG. 42B illustrates the details of the enable 1 circuit shown inFIG. 41;

[0145]FIG. 42C illustrates the details of the enable 2 circuit shown inFIG. 41;

[0146]FIG. 42D illustrates the details of the voltage detection circuitshown in FIG. 41;

[0147]FIG. 42E illustrates the details of the pullup current monitorshown in FIG. 41;

[0148]FIG. 42F illustrates the details of the pulldown current monitorshown in FIG. 41;

[0149]FIG. 42G illustrates the details of the output logic shown in FIG.41;

Center Logic (See Section VIII)

[0150]FIG. 43 is a block diagram illustrating the center logic of FIG.2;

[0151]FIG. 44 is a block diagram illustrating the RAS chain circuitshown in FIG. 43;

[0152]FIG. 45A illustrates the details of the RAS D generator circuitshown in FIG. 44;

[0153]FIG. 45B illustrates the details of the enable phase circuit shownin FIG. 44;

[0154]FIG. 45C illustrates the details of the ra enable circuit shown inFIG. 44;

[0155]FIG. 45D illustrates the details of the wl tracking circuit shownin FIG. 44;

[0156]FIG. 45E illustrates the details of the sense amps enable circuitshown in FIG. 44;

[0157]FIG. 45F illustrates the details of the RAS lockout circuit shownin FIG. 44;

[0158]FIG. 45G illustrates the details of the enable column circuitshown in FIG. 44;

[0159]FIG. 45H illustrates the details of the equilibration circuitshown in FIG. 44;

[0160]FIG. 45I illustrates the details of the isolation circuit shown inFIG. 44;

[0161]FIG. 45J illustrates the details of the read/write control circuitshown in FIG. 44;

[0162]FIG. 45K illustrates the details of the write timeout circuitshown in FIG. 44;

[0163]FIG. 45L illustrates the details of the data in latch (high)circuit shown in FIG. 44;

[0164]FIG. 45M illustrates the details of the data in latch (low)circuit shown in FIG. 44;

[0165]FIG. 45N illustrates the details of the stop equilibration circuitshown in FIG. 44;

[0166]FIG. 450 illustrates the details of the CAS L RAS H circuit shownin FIG. 44;

[0167]FIG. 45P illustrates the details of the RAS-RASB circuit shown inFIG. 44;

[0168]FIG. 46 is a block diagram illustrating the control logic shown inFIG. 43;

[0169]FIG. 47A illustrates the details of the RAS buffer circuit shownin FIG. 46;

[0170]FIG. 47B illustrates the details of the fuse pulse generatorcircuit shown in FIG. 46;

[0171]FIG. 47C illustrates the details of the output enable buffercircuit shown in FIG. 46;

[0172]FIG. 47D illustrates the details of the CAS buffer circuit shownin FIG. 46;

[0173]FIG. 47E illustrates the details of the dual CAS buffer circuitshown in FIG. 46;

[0174]FIG. 47F illustrates the details of the write enable buffercircuit shown in FIG. 46;

[0175]FIG. 47G illustrates the details of the QED logic circuit shown inFIG. 46;

[0176]FIG. 47H illustrates the details of the data out latch shown inFIG. 46;

[0177]FIG. 47I illustrates the details of the row fuse precharge circuitshown in FIG. 46;

[0178]FIG. 47J illustrates the details of the CBR circuit shown in FIG.46;

[0179]FIG. 47K illustrates the details of the pcol circuit shown in FIG.46;

[0180]FIG. 47L illustrates the details of the write enable circuit(high) shown in FIG. 46;

[0181]FIG. 47M illustrates the details of the write enable circuit (low)shown in FIG. 46;

[0182]FIGS. 48A and B are a block diagram illustrating the row addressblock shown in FIG. 43;

[0183]FIGS. 49A, 49B, and 49C illustrate the details of the row addressbuffers of FIG. 48A;

[0184]FIGS. 50A, 50B, and 50C illustrate the details of the drivers andNAND P decoders of FIG. 48B;

[0185]FIGS. 51A and 51B are a block diagram illustrating the columnaddress block shown in FIG. 43;

[0186]FIGS. 52A, 52B, 52C, and 52D illustrate the details of the columnaddress buffers and input circuits therefor of FIG. 51A;

[0187]FIG. 53 illustrates the details of the column predecoders of FIG.5IB;

[0188]FIGS. 54A and 54B illustrate the details of the 16 Meg and 32 Megselect circuits, respectively, of FIG. 51B;

[0189]FIG. 55 illustrates the details of the eq driver circuit of FIG.51B;

[0190]FIG. 56 is a block diagram illustrating the test mode logic ofFIG. 43;

[0191]FIG. 57A illustrates the details of the test mode reset circuitshown in FIG. 56;

[0192]FIG. 57B illustrates the details of the test mode enable latchcircuit shown in FIG. 56;

[0193]FIG. 57C illustrates the details of the test option logic circuitshown in FIG. 56;

[0194]FIG. 57D illustrates the details of the supervolt circuit shown inFIG. 56;

[0195]FIG. 57E illustrates the details of the test mode decode circuitshown in FIG. 56;

[0196]FIG. 57F illustrates the details of the SV test mode decode 2circuits and associated buses and the optprog driver circuit shown inFIG. 56;

[0197]FIG. 57G illustrates the details of the redundant test resetcircuit shown in FIG. 56;

[0198]FIG. 57H illustrates the details of the Vccp clamp shift circuitshown in FIG. 56;

[0199]FIG. 57I illustrates the details of the DVC2 up/down circuit shownin FIG. 56;

[0200]FIG. 57J illustrates the details of the DVC2 OFF circuit shown inFIG. 56;

[0201]FIG. 57K illustrates the details of the pass Vcc circuit shown inFIG. 56;

[0202]FIG. 57L illustrates the details of the TTLSV circuit shown inFIG. 56;

[0203]FIG. 57M illustrates the details of the disred circuit shown inFIG. 56;

[0204]FIGS. 58A and 58B are a block diagram illustrating the optionlogic of FIG. 43;

[0205]FIGS. 59A and 59B illustrate the details of the both fuse2circuits shown in FIG. 58A;

[0206]FIG. 59C illustrates the details of one of the SGND circuits shownin FIG. 58A;

[0207]FIG. 59D illustrates the ecol delay circuit and the antifusecancel enable circuit of FIG. 58A;

[0208]FIG. 59E illustrates the CGND circuits of FIG. 58B;

[0209]FIG. 59F illustrates the antifuse program enable, passgate, andrelated circuits of FIG. 58A;

[0210]FIG. 59G illustrates the bond option circuits and bond optionlogic of FIG. 58A;

[0211]FIG. 59H illustrates the laser fuse option circuits of FIG. 58B;

[0212]FIG. 59I illustrates the laser fuse opt 2 circuits and the regpretest circuit of FIG. 58B;

[0213]FIG. 59J illustrates the 4 k logic circuit of FIG. 58A;

[0214]FIGS. 59K and 59L illustrate the fuse ID circuit of FIG. 58A;

[0215]FIG. 59M illustrates the DVC2E circuit of FIG. 58A;

[0216]FIG. 59N illustrates the DVC2GEN circuit of FIG. 58A;

[0217]FIG. 590 illustrates the spares circuit shown in FIG. 43;

[0218]FIG. 59P illustrates the miscellaneous signal input circuit shownin FIG. 43;

Global Sense Amp Drivers (See Section IX)

[0219]FIG. 60 is a block diagram illustrating the global sense amplifierdriver show in FIG. 3C;

[0220]FIG. 61 is an electrical schematic illustrating one of the senseamplifier driver blocks of FIG. 60;

[0221]FIG. 62 is an electrical schematic illustrating one of the row gapdrivers of FIG. 60;

[0222]FIG. 63 is an electrical schematic illustrating the isolationdriver of FIG. 62;

Right and Left Logic (See Section X)

[0223]FIG. 64A is a block diagram illustrating the left side of theright logic of FIG. 2;

[0224]FIG. 64B is a block diagram illustrating the right side of theright logic of FIG. 2;

[0225]FIG. 65A is a block diagram illustrating the left side of the leftlogic of FIG. 2;

[0226]FIG. 65B is a block diagram illustrating the right side of theleft logic of FIG. 2;

[0227]FIG. 66 illustrates the detail of the 128 Meg driver blocks Afound in the right and left logic circuits of FIGS. 64A and 65B;

[0228]FIG. 67 is a block diagram illustrating the 128 Meg driver blocksB found in the right and left logic circuits of FIGS. 64A and 65B;

[0229]FIG. 68A illustrates the details of the row address driverillustrated in FIG. 67;

[0230]FIG. 68B illustrates the details of the column address delaycircuits illustrated in FIG. 67;

[0231]FIG. 69 illustrates the details of the decoupling elements foundin the right and left logic circuits of FIGS. 64A and 65B; FIG. 70illustrates the detail of the odd/even drivers found in the right andleft logic circuits of FIGS. 64A, 64B, 65A, and 65B;

[0232]FIG. 71A illustrates the details of the array V drivers found inthe right and left logic circuits of FIGS. 64A, 64B, 65A, and 65B;

[0233]FIG. 71B illustrates the details of the array V switches found inthe right and left logic circuits of FIGS. 64A, 64B, 65A, and 65B;

[0234]FIG. 72A illustrates the details of the DVC2 switches found in theright and left logic circuits of FIGS. 64B and 65A;

[0235]FIG. 72B illustrates the details of the DVC2Up/Down circuits foundin the right and left logic circuits of FIGS. 64B and 65A;

[0236]FIG. 73 illustrates the details of the DVC2 nor circuit found inthe right and left logic circuits of FIGS. 64A and 65B;

[0237]FIG. 74 is a block diagram illustrating the column address driverblocks found in the right and left logic circuits of FIGS. 64A, 64B,65A, and 65B;

[0238]FIG. 75A illustrates the details of the enable circuit found inFIG. 74;

[0239]FIG. 75B illustrates the details of the delay circuit found inFIG. 74;

[0240]FIG. 75C illustrates the details of the column address driversfound in FIG. 74;

[0241]FIG. 76 is a block diagram illustrating the column address driverblocks 2 found in the right and left logic circuits of FIGS. 64A, 64B,65A, and 65B;

[0242]FIG. 77 illustrates the details of the column address driversfound in FIG. 76;

[0243]FIG. 78 is a block diagram illustrating the column redundancyblocks found in the right and left logic circuits of FIGS. 64A, 64B,65A, and 65B;

[0244]FIG. 79 illustrates the details of the column banks shown in FIG.78;

[0245]FIG. 80A is a block diagram illustrating the column fuse circuitsshown in FIG. 79;

[0246]FIG. 80B illustrates the details of the output circuit shown inFIG. 80A;

[0247]FIG. 80C illustrates the details of the column fuse circuits shownin FIG. 80A;

[0248]FIG. 80D illustrates the details of the enable circuit shown inFIG. 80A;

[0249]FIG. 81A illustrates the details of the column electric fusecircuits illustrated in FIG. 79;

[0250]FIG. 81B illustrates the details of the column electric fuse blockenable circuit illustrated in FIG. 79;

[0251]FIG. 81C illustrates the details of the fuse block select circuitillustrated in FIG. 79;

[0252]FIG. 81D illustrates the details of the CMATCH circuit illustratedin FIG. 79;

[0253]FIG. 82 is a block diagram of the global column decoders found inthe right and left logic circuits of FIGS. 64A, 64B, 65A, and 65B;

[0254]FIG. 83A illustrates the details of the row driver blocks shown inFIG. 82;

[0255]FIG. 83B illustrates the details of the column decode CMAT driversshown in FIG. 82;

[0256]FIG. 83C illustrates the details of the column decode CA01 driversshown in FIG. 82;

[0257]FIG. 83D illustrates the details of the global column decodesections shown in FIG. 82;

[0258]FIG. 84A illustrates the details of the column select driversshown in FIG. 83D;

[0259]FIG. 84B illustrates the details of the R column select driversshown in FIG. 83D;

[0260]FIG. 85 is a block diagram illustrating the row redundancy blocksfound in the right and left logic circuits of FIGS. 64A, 64B, 65A, and65B;

[0261]FIG. 86 illustrates the redundant logic illustrated in the blockdiagram of FIG. 85;

[0262]FIG. 87 illustrates the details of the row banks shown in FIG. 85;

[0263]FIG. 88 illustrates the details of the rsect logic shown in FIG.87;

[0264]FIG. 89 is a block diagram illustrating the row electric blockillustrated in FIG. 87;

[0265]FIG. 90A illustrates the details of the electric banks shown inFIG. 89;

[0266]FIG. 90B illustrates the details of the redundancy enable circuitshown in FIG. 89;

[0267]FIG. 90C illustrates the details of the select circuit shown inFIG. 89;

[0268]FIG. 90D illustrates the details of the electric bank 2 shown inFIG. 89;

[0269]FIG. 90E illustrates the details of the output circuit shown inFIG. 89;

[0270]FIG. 91 is a block diagram illustrating the row fuse blocks shownin FIG. 87;

[0271]FIG. 92A illustrates the details of the fuse banks shown in FIG.91;

[0272]FIG. 92B illustrates the details of the redundancy enable circuitshown in FIG. 91;

[0273]FIG. 92C illustrates the details of the select circuit shown inFIG. 91;

[0274]FIG. 92D illustrates the details of the fuse bank 2 shown in FIG.91;

[0275]FIG. 92E illustrates the details of the output circuit shown inFIG. 91;

[0276]FIG. 93A illustrates the details of the input logic shown in theblock diagram of FIG. 87;

[0277]FIG. 93B illustrates the details of the row electric fuse blockenable circuit shown in the block diagram of FIG. 87;

[0278]FIG. 93C illustrates the details of the row electric fuse shown inthe block diagram of FIG. 87;

[0279]FIG. 93D illustrates the details of the row electric pairs shownin the block diagram of FIG. 87;

[0280]FIG. 94 illustrates the details of the row redundancy buffersfound in the right and left logic circuits of FIGS. 64A, 64B, 65A, and65B;

[0281]FIG. 95 illustrates the details of the topo decoders found in theright and left logic circuits of FIGS. 64A, 64B, 65A, and 65B;

[0282]FIG. 96 illustrates the details of the data fuse id found in theleft logic circuit of FIG. 65A;

Miscellaneous Figures (See Section XI)

[0283]FIG. 97 illustrates the array data topology;

[0284]FIG. 98 illustrates the details of one of the memory cells shownin FIG. 97;

[0285]FIG. 99 is a diagram illustrating the states of a powerup sequencecircuit which may be used to control powerup of the present invention;

[0286]FIG. 100 is a block diagram of the powerup sequence circuit andalternative components;

[0287]FIG. 101A illustrates the details of the voltage detector shown inFIG. 100;

[0288]FIGS. 101B and 101C are voltage diagrams illustrating theoperation of the voltage detector shown in FIG. 101A;

[0289]FIG. 101D illustrates the details of the reset logic shown in FIG.100;

[0290]FIG. 101E illustrates one of the delay circuits shown in FIG.101D;

[0291]FIG. 101F illustrates the details of one of the RC timing circuitsshown in FIG. 100;

[0292]FIG. 101G illustrates the details of the other of the RC timingcircuits shown in FIG. 100;

[0293]FIG. 101H illustrates the details of the output logic shown inFIG. 100;

[0294]FIG. 101I illustrates the details of the bond option shown in FIG.100;

[0295]FIG. 101J illustrates the details of the state machine circuit inFIG. 100;

[0296]FIG. 102A is a timing diagram illustrating the externally-suppliedvoltage Vccx associated with the powerup sequence circuit shown in FIG.100;

[0297]FIG. 102B is a timing diagram illustrating the signal UNDERVOLT*associated with the powerup sequence circuit shown in FIG. 100;

[0298]FIG. 102C is a timing diagram illustrating the signal CLEAR*associated with the powerup sequence circuit shown in FIG. 100;

[0299]FIG. 102D is a timing diagram illustrating the signal VBBONassociated with the powerup sequence circuit shown in FIG. 100;

[0300]FIG. 102E is a timing diagram illustrating the signal DVC2EN*associated with the powerup sequence circuit shown in FIG. 100;

[0301]FIG. 102F is a timing diagram illustrating the signal DVC2OKRassociated with the powerup sequence circuit shown in FIG. 100;

[0302]FIG. 102G is a timing diagram illustrating the signal VCCPEN*associated with the powerup sequence circuit shown in FIG. 100;

[0303]FIG. 102H is a timing diagram illustrating the signal VCCPONassociated with the powerup sequence circuit shown in FIG. 100;

[0304]FIG. 102I is a timing diagram illustrating the signal PWRRAS*associated with the powerup sequence circuit shown in FIG. 100;

[0305]FIG. 102J is a timing diagram illustrating the signal RASUPassociated with the powerup sequence circuit shown in FIG. 100;

[0306]FIG. 102K is a timing diagram illustrating the signal PWRDUP*associated with the powerup sequence circuit shown in FIG. 100;

[0307]FIG. 103 is a test mode entry timing diagram;

[0308]FIG. 104 is a timing diagram illustrating the ALLROW high andHALFROW high test modes;

[0309]FIG. 105 is a timing diagram illustrating the output ofinformation when the chip is in a test mode;

[0310]FIG. 106 is a timing diagram illustrating the timing of theREGPRETM test mode;

[0311]FIG. 107 is a timing diagram illustrating the timing of theOPTPROG test mode;

[0312]FIG. 108 is reproduction of FIG. 4 illustrating an array slice tobe discussed in connection with the all row high test mode;

[0313]FIG. 109 is a reproduction of FIG. 6A with the sense amps and therow decoders illustrated for purposes of explaining the all row hightest mode;

[0314]FIG. 110 identifies various exemplary dimensions for the chip ofthe present invention;

[0315]FIG. 111 illustrates the bonding connections between the chip andthe lead frame;

[0316]FIG. 112 illustrates a substrate carrying a plurality of chipsconstructed according to the teachings of the present invention; and

[0317]FIG. 113 illustrates the DRAM of the present invention used in amicroprocessor based system.

Microfiche Appendix

[0318] Reference is hereby made to an appendix which contains ninemicrofiche having a total of fifty-two frames. The appendix contains 33drawings which illustrate substantially the same information as is shownin FIGS. 1-113, but in a more connected format.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0319] For convenience, this Description of the Preferred Embodiments isdivided into the following sections:

[0320] I. Introduction

[0321] II. 256 Meg DRAM Architecture

[0322] III. Array Architecture

[0323] IV. Data and Test Paths

[0324] V. Product Configuration and Exemplary Design Specifications

[0325] VI. Bus Architecture

[0326] VII. Voltage Supplies

[0327] VIII. Center Logic

[0328] IX. Global Sense Amp Drivers

[0329] X. Right and Left Logic

[0330] XI. Miscellaneous Figures

[0331] XII. Conclusion

[0332] I. Introduction

[0333] In the following description, various aspects of the disclosedmemory device are depicted in different figures, and often the samecomponent is depicted in different ways and/or different levels ofdetail in different figures for the purposes of describing variousaspects of the present invention. It is to be understood, however, thatany component depicted in more than one figure retains the samereference numeral in each.

[0334] Regarding the nomenclature to be used herein, throughout thisspecification and in the figures, “CA<x>” and “RA<y>” are to beunderstood as representing bit x of a given column address and bit y ofa given row address, respectively. References to DLa<0>, DLb<0>, DLc<0>,and DLd<0> will be understood to represent the least significant bit ofan n bit byte coming from four distinct memory locations.

[0335] It is to be understood that the various signal line designationsare used consistently in the figures, such that the same signal linedesignation (e.g., “Vcc”, “CAS,” etc. . . .) appearing in two or morefigures is to be interpreted as indicating a connection between thelines that they designate in those figures, in accordance withconventional practice relating to schematic, wiring, and/or blockdiagrams. Finally, a signal having an asterisk indicates that thatsignal is the logical complement of the signal having the samedesignation but without the asterisk, e.g., CMAT* is the logicalcomplement of the column match signal CMAT.

[0336] There are a number of voltages used through the DRAM of thepresent invention. The production of those voltages is described indetail in Section VII—Supply Voltages. However, the voltages appearthroughout the figures and in some instances are discussed inconjunction with the operation of specific circuits prior to SectionVII. Therefore, to minimize confusion, the various voltages will now beintroduced and defined.

[0337] Vccx—externally supplied voltage

[0338] Vccq—power for the data output pad drivers

[0339] Vcca—array voltage (produced by voltage regulator 220 shown inFIG. 35)

[0340] Vcc—peripheral voltage (produced by voltage regulator 220 shownin FIG. 35)

[0341] Vccp—boosted version of Vcc used for biasing the wordlines(produced by the Vccp pump 400 shown in FIG. 39)

[0342] Vbb—back bias voltage (produced by the Vbb pump 280 shown in FIG.37)

[0343] Vss—nominally ground (externally supplied)

[0344] Vssq—ground for the data output pad drivers

[0345] DVC2—one half of Vcc used for biasing the digitlines (produced bythe DVC2 generators 500-507 shown in FIG. 41)

[0346] AVC2—one half of Vcc used as the cellplate voltage (has the samevalue as DVC2)

[0347] The prefix “map” before a voltage or signal indicates that thevoltage or signal is switched, i.e., it can be turned on or off.

[0348] Certain of the components and/or signals identified in thedescription of the preferred embodiment are known in the industry byother names. For example, the conductors in the array which are referredto in the Description of the Preferred Embodiments as digitlines aresometimes referred to in the industry as bitlines. The term “column”actually refers to two conductors which comprise the column. Anotherexample is the conductor which is referred to herein as a rowline. Thatconductor is also known in the industry as a wordline. Those of ordinaryskill in the art will recognize that the terminology used herein is usedfor purposes of explaining exemplary embodiments of the presentinvention and not for limiting the same. Terms used in this document areintended to include the other names by which signals or parts arecommonly known in the industry.

[0349] II. 256 Meg DRAM Architecture

[0350]FIG. 2 is a high level block diagram illustrating a 256 Meg DRAM10 constructed according to the teachings of present invention. Althoughthe following description is specific to this presently preferredembodiment of the invention, it is to be understood that thearchitecture and circuits of the present invention may be advantageouslyapplied to semiconductor memories of different sizes, both larger andsmaller in capacity. Additionally, certain circuits disclosed herein,such as the powerup sequence circuit, voltage pumps, etc. may find usesin circuits other than memory devices.

[0351] In FIG. 2, the chip 10 is comprised of a main memory 12. Mainmemory 12 is comprised of four equally sized array quadrants numberedconsecutively, beginning with array quadrant 14 in the upper right handcorner, array quadrant 15 in the bottom right hand corner, arrayquadrant 16 in the bottom left hand corner, and array quadrant 17 in theupper left hand corner. Between array quadrant 14 and array quadrant 15is situated right logic 19. Between the array quadrant 16 and the arrayquadrant 17 is situated left logic 21. Between the right logic 19 andthe left logic 21 is situated center logic 23. The center logic 23 isdiscussed in greater detail hereinbelow in Section VIII. The right andleft logic 19 and 21, respectively, are described in greater detailhereinbelow in Section X.

[0352] The array quadrant 14 is illustrated in greater detail in FIGS.3A-3E. Each of the other array quadrants 15, 16, 17, is identical inconstruction and operation to the array quadrant 14. Therefore, only thearray quadrant 14 will be described in detail.

[0353] The array quadrant 14 is comprised of a left 32 Meg array block25 and a right 32 Meg array block 27. The array blocks 25 and 27 areidentical. The signals destined for or output from left 32 Meg arrayblock 25 carry an L in their designation whereas the signals destinedfor or output from right 32 Meg array block 27 carry an R in theirdesignation. A global sense amp driver 29 is located between left arrayblock 25 and right array block 27. Returning briefly to FIG. 2, thearray quadrant 15 is comprised of a left 32 Meg array block 31, a right32 Meg array block 33, and a global sense amp driver 35. Array quadrant16 is comprised of a left 32 Meg array block 38, a right 32 Meg arrayblock 40, and a global sense amp driver 42. Array quadrant 17 iscomprised of a left 32 Meg array block 45, a right 32 Meg array block47, and a global sense amp driver 49. Because there are two 32 Meg arrayblocks in each of the four array quadrants, there are thus eight 32 Megarray blocks carried on the chip 10.

[0354] It is seen from FIG. 3A that the left 32 Meg array 25 can bephysically disconnected from the various voltage supplies that supplyvoltage to the array 25 by controlling the condition of switches 48. Theswitches 48 control the application of the switched array voltage(mapVcca), the switched, boosted, array voltage (mapVccp), (the switch48 associated with mapvccp is not shown in the figure), the switcheddigitline bias voltage (mapDVC2), and the switched, cellplate biasvoltage (mapAVC2). The 32 Meg array 25 also includes one or moredecoupling capacitors 44. The purpose of the decoupling capacitors is toprovide a capacitive load for the voltage supplies as will be describedhereinbelow in greater detail in Section VII. For now, it is sufficientto note the that the decoupling capacitor 44 is located on the oppositeside of the switch from the voltage supplies. The right 32 Meg array 27,and all the other 32 Meg arrays 31, 33, 38, 40, 45, and 47 are similarlyprovided with decoupling capacitors 44 and switched versions of thearray voltage, boosted array voltage, digitline bias voltage, andcellplate bias voltage.

[0355] III. Array Architecture

[0356]FIG. 4 is a block diagram of the 32 Meg array block 25 whichillustrates an 8×16 array of individual arrays 50, each 256 k, whichmake up the 32 Meg array block 25. Between each row of individual arrays50 are positioned sense amplifiers 52. Between each column of individualarrays 50 are positioned row decoders 54. In the gaps, multiplexers 55are positioned. The portion of the figure shaded in FIG. 4 isillustrated in greater detail in FIG. 5.

[0357] In FIG. 5, one of the individual arrays 50 is illustrated. Theindividual array 50 is serviced by a left row decoder 56 and a right rowdecoder 58. The individual array 50 is also serviced by a “top” N-Psense amplifier 60 and a “bottom” N-P sense amplifier 62. A top senseamp driver 64 and a bottom sense amp driver 66 are also provided.

[0358] Between the individual array 50 and the N-P sense amp 60 are aplurality of digit lines, two of which 68, 68′ and 69, 69′ are shown. Asis known in the art, the digitlines extend through the array 50 and intothe sense amp 60 The digitlines are a pair of lines with one of thelines carrying a signal and the other line carrying the complement ofthe signal. It is the function of the N-P sense amp 60 to sense adifference between the two lines. The sense amplifier 60 also servicesthe 256 k array located above the array 50, which is not shown in FIG.5, via a plurality of digitlines, two of which, 70, 70′ and 77, 71′, areshown. The upper N-P sense amp 60 places the signals sensed on thevarious digitlines onto I/O lines 72, 72′, 74, 74′. (Like thedigitlines, the I/O lines designated with a prime carry the complementof the signal carried by the I/O line bearing the same reference numberbut without the prime designation.) The I/O lines run throughmultiplexers 76, 78 (also referred to as muxes). The mux 76 takes thedata on the I/O lines 72, 72′, 74, 74′ and places the data on datalines.Datalines 79, 79′, 80, 80′, 81, 81′, 82, 82′ are responsive to mux 76.(The same designation scheme used for the I/O lines applies to thedatalines, e.g., dataline 79′ carries the complement of the signalcarried on dataline 79.)

[0359] In a similar fashion, N-P sense amp 62 senses signals on thedigitlines represented generally by reference numbers 86, 87 and placessignals on I/O lines represented generally by reference No. 88 which arethen input to multiplexers 90 and 92. The multiplexer 90, like themultiplexer 76, places signals on the datalines 79, 79′, 80, 80′, 81,81′, 82, 82′.

[0360] The 256 k individual array 50 illustrated in the block diagram ofFIG. 5 is illustrated in detail in FIG. 6A. The individual array 50 iscomprised of a plurality of individual cells which may be as describedhereinabove in conjunction with FIG. 1. The individual array 50 mayinclude a twist, represented generally by reference number 84, as iswell known in the art. Twisting improves the signal-to-noisecharacteristics. There are a variety of twisting schemes used in theindustry, e.g., single standard, triple standard, complex, etc., any ofwhich may be used for the twist 84 illustrated in FIG. 6A. (The readerseeking more detail regarding the construction of the array 50 isdirected to FIG. 97 which is a topological view of the array 50, and thedescription associated therewith, and FIG. 98, which is a view of acell, and the description associated therewith.)

[0361]FIG. 6B illustrates the row decoder 56 illustrated in FIG. 5. Thepurpose of the row decoder 56 is to fire one of the wordlines withinindividual array 50 which is identified in address information receivedby the chip 10. The use of local row decoders enables sending the fulladdress and eliminates a metal layer. Those of ordinary skill in the artwill understand the operation of the row decoder 56 from an examinationof FIG. 6B. However, it is important to note that the RED (redundant)line runs through the sense amp 60 in metal 2, and is input to an lphdriver circuit 96 and a redundant wordline driver circuit 97 in rowdecoder 56 for the purpose of turning off the normal wordline andturning on the redundant wordline.

[0362]FIG. 6C illustrates the sense amplifier 60 shown in FIG. 5 indetail. The purpose of the sense amplifier 60 is to sense the differencebetween, for example, digitline 68, 68′ to determine if the storageelement whose wordline is fired and that is connected to digitline 68,68′ has a logic “1” or a logic “0” stored therein. In the designillustrated in FIG. 6C, the sense amps are located inside isolationtransistors 83. It is necessary to gate the isolation transistors 83with a sufficiently high voltage to enable the isolation transistors 83to conduct a full Vcc to enable a write of a full “one” into the device.It is, thus, necessary to gate the transistors 83 high enough to passthe voltage Vcc and not the voltage Vcc-Vth. Therefore, the boostedvoltage Vccp is used to gate the isolation transistors 83. The operationof the sense amplifier 60 will be understood by those of ordinary skillin the art from an examination of FIG. 6C.

[0363]FIG. 6D illustrates the array multiplexer 78 and the sense ampdriver 64 shown in FIG. 5 in detail. As previously mentioned, thepurpose of the multiplexer 78 is to determine which signals available onthe array's I/O lines are to be placed on the array's datalines. Thatmay be accomplished by programming the switches in the area generallydesignated 63. Such “softswitching” allows for different types ofmapping without requiring hardware changes. The sense amp driver 64provides known control signals, e.g. ACT, ISO, LEQ, etc., to N-P senseamplifier 60. From the schematic illustrated in FIG. 6D, theconstruction and operation of the array multiplexer 78 and sense ampdriver 64 will be understood.

[0364] IV. Data and Test Paths

[0365] The data read path begins, of course, in an individual storageelement within one of the 256 k arrays. The data in that element issensed by an N-P sense amplifier, such as sense amplifier 60 in FIG. 6C.Through proper operation of the I/O switches 85 within N-P senseamplifier 60, that data is then placed on I/O lines 72, 72′, 74, 74′.Once on the I/O lines, the data's “journey” to the output pads of thechip 10 begins.

[0366] Turning now to FIG. 7, the 32 Meg array 25 shown in FIG. 4 isillustrated. In FIG. 7, the 8×16 array of 256 k individual arrays 50 isagain illustrated. The lines running vertically in FIG. 7 between thecolumns of arrays 50 are data lines. Recall from FIG. 5 that the rowdecoders are also positioned between the columns of individual arrays50. In FIG. 6B, the detail is illustrated as to how the datalines routethrough the row decoders. In that manner, the row decoders are used forwordline driving as is known in the art, and to provide “streets” fordataline routing to the peripheral circuits.

[0367] Returning to FIG. 7, the lines running horizontally between rowsof individual arrays 50 are the I/O lines. The I/O lines must routethrough the sense amplifiers, as shown in FIG. 6C, because the senseamplifiers are also located in the space between the rows of arrays 50.Recall that it is the function of the multiplexers as describedhereinabove in conjunction with FIG. 5 to take signals from the I/Olines and place them on the datalines. The positioning of themultiplexers within the array 25 is illustrated in FIG. 7. In FIG. 7,nodes 94 indicate the positioning of a multiplexer of the type shown inFIG. 6D at an intersection of the I/O lines with the datalines. As willbe appreciated from an examination of FIG. 7, the I/O lines, which routethrough the sense amplifiers, extend across two arrays 50 before beinginput to a multiplexer. That architecture permits a 50% reduction in thenumber of data muxes required in the gap cells. The data muxes arecarefully programmed to support the firing of only two rows, separatedby a predetermined number of arrays, per 32 Meg block without datacontention on the datalines. For example, rows may be fired in arrays 0and 8, 1 and 9, etc. Both fire and repairs are done on the sameassociated groups. Additionally, as previously mentioned, thearchitecture of the present invention routes the redundant wordlineenable signal (shown in FIG. 6B) through the sense amp strip in metal 2to ensure quick deselection of the normal row. Finally, normal phaselines are remapped, as shown in FIG. 61, to appropriate redundantwordline drivers for efficient reuse of signals.

[0368] The architecture illustrated in FIG. 7 is, of course, repeated inthe other 32 Meg array blocks 27, 31, 33, 38, 40, 45, 47. Use of thearchitecture illustrated in FIG. 7 allows the data to be routed directlyto the peripheral circuits which shortens the data path and speeds partoperation. Second, doubling the I/O line length by appropriatelypositioning the multiplexers simplifies the gap cell layout and providesa convenient framework for 4 k operation, i.e., two rows per 32 Megblock. Third, sending the RED signal through the sense amp is fasterwhen combined with the phase signal remapping discussed above.

[0369] After the data has been transferred from the I/O lines to thedata lines, that data is next input to an array I/O block 100 as shownin FIG. 8. The array I/O block 100 services the array quadrant 14illustrated in FIG. 2. In a similar fashion, an array I/O block 102services array quadrant 15; an array I/O block 104 services arrayquadrant 16; an array I/O block services array quadrant 17. Thus, eachof the array I/O blocks 100, 102, 104, 106 serves as the interfacebetween the 32 Meg array blocks in each of the quadrants and theremainder of the data path illustrated in FIG. 8.

[0370] In FIG. 8, after the array I/O blocks, the next element in thedata read path is a data read mux 108. The data read mux 108 determinesthe data to be input to an output data buffer 110 in response to controlsignals produced by a data read mux control circuit 112. The output databuffer 110 outputs the data to a data pad driver 114 in response to adata out control circuit 116. The data pad driver 114 drives a data padto either Vccq or Vssq to represent a logic level “1” or a logic level“0”, respectively, on the output pad.

[0371] With respect to the write data path, that data path includes adata in buffer 118 under the control of a data in buffer control circuit120. Data in the data in buffer 118 is input to a data write mux 122which is under the control of a data write mux control circuit 124. Fromthe data write mux 122, the input data is input to the array I/O blocks100, 102, 104, 106 and ultimately written into array quadrants 14, 15,16, 17, respectively, according to address information received by chip10.

[0372] The data test path is comprised of a data test block 126 and adata path test block 128 connected between the array I/O blocks 100,102, 104, 106 and the data read mux 108.

[0373] Completing the description of the block diagram of FIG. 8, a dataread bus bias circuit 130, a DC sense amp control circuit 132, and adata test DC enable circuit 134 are also provided. The circuits 130,132, and 134 provide control and other signals to the various blocksillustrated in FIG. 8. Each of the blocks illustrated in FIG. 8 will nowbe described in more detail.

[0374] One of the array blocks 100 is illustrated in block diagram formin FIG. 9 and as a wiring schematic in FIGS. 10A-10D. The I/O block 100is comprised of a plurality of data select blocks 136. An electricalschematic of one type of data select block 136 that may be used isillustrated in FIG. 11. In FIG. 11, the EQIO line is fired when thecolumns are to be charged or for a write recovery. When the twotransistors 137 and 138 are conductive, the voltage on the lines LIOAand LIOA* are clamped to one Vth below Vcc.

[0375] Returning to FIG. 9, the I/O block 100 is also comprised of aplurality of data blocks 140 and data test comp circuits 141. The datatest comp circuits 141 are described hereinbelow in conjunction withFIG. 25. A type of data block 140 that may be used is shown in detail inthe electrical schematics of FIGS. 12A and 12B. The data blocks 140 maycontain, for example, a write driver 142 illustrated in FIG. 12A, and aDC sense amp 143 illustrated in FIG. 12B. The write driver 142 is partof the write data path while the DC sense amp 143 is part of the dataread path.

[0376] The write driver 142, as the name implies, writes data intospecific memory locations. The write driver 142 is connected to only oneset of I/O lines, although multiple sets of I/O lines may be fed by asingle write driver circuit via muxes. The write driver 142 uses atri-state output stage to connect to the I/O lines. Tri-state outputs renecessary because the I/O lines are used for both read and writeoperations. The write driver 142 remains in a high impedance stateunless the signal labeled WRITE is high, indicating a write operation.As shown in FIG. 12A, the write driver 142 is controlled by specificcolumn addresses, the WRITE signal, and Data Write (DW) Signal.

[0377] The write driver 142 also receives topinv and topinv*. Thepurpose of the topo signals is to ensure that a logical one is writtenwhen a logical one is input to the part. The topo decoder circuit, whichproduces the topo signals, knows what m-bits are connected to the digitand digit* lines. The topo decoder circuit is illustrated in FIG. 95.Each array I/O block gets four topo signals.

[0378] The drive transistors are sized large enough to ensure a quick,efficient, write operation, which is important because the array senseamplifiers usually remain on during a write cycle. The signals placed onthe IOA, IOA* lines in FIG. 12A are the signals (LIOA, LIOA*) input tothe data select block 136 as illustrated in the upper left hand cornerof FIG. 11.

[0379] The DC sense amplifier 143 illustrated in FIG. 12B is sometimesreferred to as a data amplifier or read amplifier. Such an amplifier isan important component even though it may take a variety ofconfigurations. The purpose of the DC sense amp 143 is to provide a highspeed, high gain, differential amplifier for amplifying very small readsignals appearing on the I/O lines into full CMOS data signals used inthe data read mux 108. In most designs, the I/O lines connected to thesense amplifiers are very capacitive. The array sense amplifiers havevery limited drive capability and are unable to drive those linesquickly. Because the DC sense amp has a very high gain, it amplifieseven the slightest separation of the I/O lines into full CMOS levels,essentially gaining back any delay associated with the I/O lines. Theillustrated sense amp is capable of outputting full rail-to-rail signalswith input signals as small as 15 mV.

[0380] As illustrated in FIG. 12B, the DC sense amp 143 consists of fourdifferential pair amplifiers and self biasing CMOS stages 144, 144′,145, 145′. The differential pairs are configured as two sets of balancedamplifiers. The amplifiers are built with an NMOS differential pairusing PMOS active loads and nMOS current mirrors. Because the nMOStransistors have higher mobility providing for smaller transistors andlower parasitic loads, nMOS amplifiers usually provide faster operationthan pMOS amplifiers. Furthermore, Vth matching is usually better fornMOS transistors providing for a more balanced design. The first set ofamplifiers is fed with the signals from the I/O lines from the array(IOA*, IOA) while the second set of amplifiers is fed with outputsignals from the first pair labeled DAX, DAX*. Bias levels into eachstage are carefully controlled to provide optimum performance.

[0381] The outputs from the second stage, labeled DAY, feed into selfbiasing CMOS inverter stages 147, 147′ which provide for fast operation.The final output stage is capable of tri-state operation to allowmultiple sets of DC sense amps to drive a given set of data read lines(DR <n>and DR* <n>). The entire DC sense amplifier 143 is equilibratedprior to operation, including the self-biasing CMOS inverter stages 147,147′, by the signals labeled EQSA, EQSA*, and EQSA2. Equilibration isnecessary to ensure that the DC sense amplifier 143 is electricallybalanced and properly biased before the input signals are applied. TheDC sense amplifier 143 is enabled whenever the enable sense amp signalENSA* is brought low, turning on the output stage and the current mirrorbias circuit 148 (seen in FIG. 12A), which is connected to thedifferential amplifiers via the signal labeled CM.

[0382] In FIG. 12B, the production of the signals DRT and DRT* is shownin the left-hand portion of the figure. The signals DRT and DRT* areused for data compression testing and cause the normal data path to bebypassed.

[0383] The data block 140 requires a number of control signals to ensureproper operation. Those signals are generated by the DC sense ampcontrol circuit 132 illustrated in FIG. 8. The details of the DC senseamp control circuit 132 are shown in the electrical schematics of FIGS.13A and 13B. In FIGS. 13A and 13B, a number of signals are receivedwhich, through the proper combination of logic gates as shown in thefigure, are combined to produce the necessary control signals for thedata block 140. It is seen in FIG. 13A that the DC sense amp controlcircuit 132 includes a mux decode A circuit 150 and a mux decode Bcircuit 151. Electrical schematics of one type of such circuits whichmay be utilized are provided in FIGS. 14 and 15, respectively. Muxdecode A circuit 150 and mux decode B circuit 151 use row addresses todetermine which datalines from the array will be used for read/writeaccess in each array block. Thus, the mux decode A circuit 150 and themux decode B circuit 151 produce signals for controlling the muxes foundwithin the array IO blocks 100, 102, 104, and 106.

[0384] The purpose of the data blocks 140 when in the read mode is toplace data coming from the data select blocks 136 from the data linescoming out of the array onto the lines which feed into the data read mux108 of FIG. 8. The data read mux 108 is illustrated in detail in FIGS.16A, 16B, and 16C. The purpose of the data read muxes is to provide morepart flexibility by enabling data output buffer 110 to be responsive tomore data. For example, for ×16 operation, each output buffer 110 hasaccess to only one data read (DR) line pair. For ×8 operation, the eightoutput buffers 110 each have two pairs of data read lines available,doubling the quantity of mbits accessible by each output buffer.Similarly, for ×4 operation, the four output buffers have four pairs ofdata read lines available, again doubling the quantity of mbitsavailable for each output. For those configurations with multiple pairsavailable, address lines control which data read line pair is connectedto a data buffer.

[0385] The data read mux 108 receives control signals from data read muxcontrol circuit 112, an electrical schematic of one type beingillustrated in FIG. 17. The purpose of the data read mux control circuit112 is to produce control signals to enable data read mux 108 to operateso as to select the appropriate data signals for output to data buffer110. Note in FIG. 17 the change in signal notation from DR for the inputsignals to LDQ for the output signals of the Mux 108.

[0386] An electrical schematic of data buffer 110 is provided in FIG.18. The control signals used to control the operation of the data outputbuffer 110 are generated by the data output control circuit 116, anelectrical schematic of which is illustrated in FIG. 19. The data outputcontrol circuit 116 is one type which may be employed; other types ofcontrol circuits may be used.

[0387] Returning to FIG. 18, the data output buffer 110 is comprised ofa latch circuit 160 for receiving data which is to be output. The latchcircuit 160 frees the DC sense amp 143 and other circuits upstream toget subsequent data for output. The input to the latch is connected tothe LQD, LQD* signals coming from the data read mux 108. Latch circuits160 appear in a variety of forms, each serving the needs of a specificapplication or architecture. The data path may, of course, containadditional latches in support of special modes of operation, such asburst mode.

[0388] A logic circuit 162 is responsive to the latch 160 forcontrolling the condition, conductive or nonconductive, of a pluralityof drive transistors in a drive transistor section 164. By properoperation of the drive transistors in drive transistor section 164, apullup terminal 167 can be pulled up to the voltage Vcc and a pulldownterminal 183 can be pulled down to ground. The signals PUP and PDNavailable at terminals 167 and 183, respectively, are used to controlthe data pad driver 114 shown in FIG. 20. If both the PUP terminal andthe PDN terminal are pulled low, a tri-state or high impedance conditionresults.

[0389] To ensure sufficient voltage is available at the gate of theoutput drive transistor responsible for pulling the PUP terminal up, aboot capacitor 168 is used. To charge the boot capacitor 168 and also toavoid the effects of inherent leakage, the capacitor 168 is held at itsbooted up or fully charged level by a holding transistor 170. Theholding transistor is connected to the boosted voltage Vccp, which isgreater than the voltage Vcc, and which may be developed by a voltagepump of the type described hereinbelow. Upon a change of state, the bootcapacitor 168 is unbooted. In prior art circuits, because of transienteffects, the holding transistor 170 was prone to continue to conduct anddraw power from the voltage pump although the boot capacitor wasunbooted, or in the process of being unbooted. That condition isundesirable, and this aspect of the present invention addresses andsolves that problem by providing a self-timed path 172. The self-timedpath ensures the boot capacitor 168 is not unbooted until the holdingtransistor 170 is completely off.

[0390] The self-timed circuit path 172 is connected between the gate oftransistor 170 and the low side of the boot capacitor 168. The path 172is comprised of an inverter 174 having its input terminal connected tothe gate of the transistor 170 and having its output terminal connectedto one of the input terminals of a NAND gate 176. In that manner, thegate potential of the holding transistor 170 is continually monitoredand fed into the NAND gate 176. An output terminal of the NAND gate 176is connected to the low side of the boot capacitor 168. The path 172 isreferred to as being self-timed because it operates directly in responseto the condition of the transistor 170 rather than relying upon somearbitrary time delay.

[0391] A second input terminal of the NAND gate 176 is connected to anoutput terminal of an inverter 178. The inverter 178 is part of thelogic circuit 162 and is in the path between the latch 160 and the gateterminal of a PUP transistor 166. The inverter 178 directly controls thestate of PUP transistor 166 and, therefore, the state of the terminal167. The PUP transistor 166 may be a PMOS transistor with the voltage ofthe boot capacitor being used to ensure that the voltage output issufficient to drive the transistor in the data pad driver 114. When theholding transistor 170 is on, a logic “1” is input to the inverter 174causing a logic “0” to appear at the first input terminal of the NANDgate 176. With a logic “0” at the first input terminal, the signalavailable at the output terminal is high and the signal available at thesecond input terminal does not matter.

[0392] When the signal available at an output terminal of the inverter178 goes high thereby shutting off PUP transistor 166, a logic “1” isinput to the second input terminal of NAND gate 176. That logic “1” alsopropagates through the circuitry illustrated in the upper portion ofFIG. 18 and becomes a logic “0” which turns off transistor 170. Thelogic “0” which turns off transistor 170 is input to inverter 174 suchthat a logic “1” is input to the first input terminal of NAND gate 176.With the input signals at both input terminals now high, the signalavailable at the output terminal of the NAND gate 176 goes low allowingthe capacitor 168 to unboot.

[0393] A string of transistors 190, 192, 194, 196, and 198 act as abuffer clamp circuit for limiting the maximum voltage on boot capacitor168. A transistor 199 is connected to the peripheral voltage Vcc forprecharging the boot capacitor 168 prior to the operation of holdingtransistor 170 and the application of the boosted voltage Vccp. Anoptional feature illustrated in FIG. 18 is that the pullup terminal 167may be additionally regulated through a switch 180 so that a PUPpulldown transistor 182 is subject to self-timing according to the stateof the signal at the bottom of the boot capacitor 168.

[0394] The terminal 167, a terminal 181, and the terminal 183 areelectrically connected to the data pad driver 114, an electricalschematic of which is illustrated in FIG. 20. The data pad driver 114drives a data output/data input pad DQn. The data output/data input padDQn represents the end of the data output path.

[0395] A data read bus bias circuit 130 is illustrated in detail in FIG.21. The purpose of the data read bus bias circuit 130 is to keep the DRlines from floating when not in use. When the EQSA* signal disables thesense amps, the circuit 130 monitors that condition and holds the DRlines at a predetermined voltage.

[0396] The data write path begins at an input/output pad and continueswith the data in buffer 118 which is under control of the data in bufferenable control circuit 120 which are both illustrated in FIG. 22. Thebuffer 118 is comprised primarily of a latch as shown in the figure. Fora DRAM that is 8 bits wide (×8), there will be eight input buffers, eachdriving into one or more write drivers through a signal labeled DW<n>(Data Write where n corresponds to the specific data bit 0-15). Thedata in buffer enable control circuit 120 produces control signalsaccording to the type of part.

[0397] In the present invention, the data write mux 122, illustrated inFIG. 23, is provided. While some DRAM designs connect the input bufferdirectly to the write driver circuits, a block of data write muxesbetween the input buffers and the write drivers allows the DRAM designto support multiple configurations such as ×4, ×8, and ×16. As shown inFIG. 23, the muxes are programmed according to the bond option controlsignals labeled OPT×4, OPT×8, and OPT×16. For ×16 operation, each inputbuffer 110 is muxed to only one set of DW lines. For ×8 operation, eachinput buffer is muxed to two sets of DW lines, essentially doubling thequantity of mbits available to each input buffer. For ×4 operation, eachinput buffer is muxed to four sets of DW lines, again doubling thenumber of mbits available to the remaining four operable input buffers.Essentially, as the quantity of input buffers is reduced, the amount ofcolumn address space is increased for the remaining buffers.

[0398] The data write mux 122 is under the control of the data write muxcontrol circuit 124 which is illustrated in detail in FIG. 24. In FIGS.23 and 24, note the change in notation between the signals input to thedata write mux 122 (DIN) and the signals output from data write mux 122(DW).

[0399] From the data write mux 122, the data to be written is input tothe write driver 142 within data block 140, described hereinabove inconjunction with FIG. 12A, where the DW signal is input in the upperleft hand corner of FIG. 12A. The write driver 142 places the data to bewritten on the I/O lines which allow the signals to work their way backinto the array through the sense amplifiers.

[0400] Now that the data read and data write paths have been described,our attention will now turn to compression issues. Address compressionand data compression are two special test modes supported by the testpath design. DRAM designs include test paths to extend testcapabilities, speed component testing, or subject a part to conditionsthat are not seen during normal operation. Compression test modes yieldshorter test times by allowing data from multiple array locations to betested and compressed on chip, thereby reducing the effective memorysize by a factor of 128 or more in some cases. Address compressionusually on the order of 4× to 32×, is accomplished by internallytreating certain address bits as “don't care” addresses. The data fromall of the don't care address locations, which correspond to specific DQpins, are compared together with special match circuits. Match circuitsare usually realized with NAND and NOR logic gates. The match circuitsdetermine if the data from each address location is the same, reportingthe result on the respective DQ pin as a match or a fail. The data pathmust be designed to support the desired level of data compression. Thatmay necessitate more DC sense amp circuits, logic, and other pathwaysthan those necessary for normal operation.

[0401] The second form of test compression is data compression, i.e.,combining data upstream of the output drivers. Data compression usuallyreduces the number of DQ pins to four, which reduces the number oftester pins required for each part and increases through-put by allowingadditional parts to be tested in parallel. Therefore ×16 partsaccommodate 4× data compression and ×8 parts accommodate 2× datacompression. The cost of any additional circuitry to implement addressand data compression must be balanced against cost benefits derived fromtest time reduction. It is also important that operation in test modeachieve 100% correlation to operation in non-test mode. Correlation isoften difficult to achieve, however, because additional circuitry mustbe activated during compression, which modifies the noise and powercharacteristics on the die.

[0402] In the description of FIGS. 25, 26, 27, 28, and 29, we addressprimarily the issue of data compression. The issue of addresscompression is additionally dealt with hereinbelow.

[0403] In FIG. 25, one of the data test comparison circuits 141 found inthe array I/O block 100 is illustrated. The circuit 141 receives a testsignal from a data test DC enable circuit 134 also seen in FIG. 8. Thepurpose of the data test comparison circuit 141 is to provide a firstlevel of comparison.

[0404] The signals output by the various array I/O blocks 100, 102, 104,106 are input to the data test block b 126 illustrated in the center ofFIG. 26. The purpose of the data test block b 126 is to provide someadditional compression and to reduce the number of tracks which must beprovided. The output of the data test block b 126 is input to the datapath test block 128, which is illustrated in detail in FIG. 27. As seenin FIG. 27, the data test block 128 is constructed of two types ofcircuits, a data test DC21 circuit 186 and a data test BLK circuit 188.One type of data test DC21 circuit 186 is shown in detail in FIG. 28,which facilitates data and address compression, while one type of datatest BLK circuit 188 is illustrated in detail in FIG. 29, whichfacilitates address compression. Each of the circuits 186, 188 performscompression and comparison of the various input signals so as to produceat the output of the data path test block 128 a data read signal (DR,DR*) suitable for input to the data read mux 108. Through thecombination of the foregoing circuits which comprise the test data path,data compression and the benefits flowing therefrom as discussed aboveare achieved.

[0405] V. Product Configuration and Exemplary Design Specifications

[0406] The memory chip 10 of the present invention may be configured toprovide parts of varying size. FIG. 30 illustrates the mapping of theaddress bits to the 256 Meg array so as to provide ×16, ×8, and ×4operation. Illustrated in FIG. 30 is the mapping for each of the 32 Megarray blocks 25, 27, 31, 33, 38, 40, 45, 47 for various types ofoperation. For example, for ×16 operation, the array block 45 is dividedinto four sections for storage of DQ0, DQ1, DQ2, DQ3, DQ4, DQ5, DQ6, andDQ7. If the chip 10 were configured for ×8 operation, the same arrayblock 45 would be mapped to provide storage for only DQ0, DQ1, DQ2, andDQ3. If the chip 10 were configured for ×4 operation, the array block 45would be mapped so as to provide storage for only DQ0 and DQ1. The otherarray blocks are similarly mapped as shown in FIG. 30.

[0407] The different part configurations are primarily a function of thevarious muxes provided in the read and write data paths as describedhereinabove. Part configurations may be selected through bond options,which are “read” by the various logic circuits. The bond options for thepresent preferred embodiment are illustrated in Table 3 below. There areonly two bond option pads. The logic circuits produce control signalsfor controlling the muxes and other components based on the selectedpart configuration. TABLE 3 Bond Options OPTBPAD OPTAPAD MODE N/C N/CX16  N/C VCC X4 VCC N/C X8 VCC VCC X8

[0408] For each configuration, the amount of array sections available toan input buffer must change. By using data write muxes as describedhereinabove to drive as few or as many write driver circuits asrequired, design flexibility is easily accommodated. The pinconfigurations corresponding to operation as a ×16, ×8, and ×4 part areillustrated in FIGS. 31A, 31B, and 31C.

[0409] Regardless of the product configuration, all data is stored andretrieved from the main array 12. The part is designed so that all datain the 256 Meg main array 12 can be located by bit column addresses andbit row addresses, the number of which is dependent on part size ortype.

[0410]FIG. 32A illustrates one column address mapping scheme for the 256Meg main array 12. Column address CA_(—)9<0:1>selects between the bottom64 Meg quadrants 15 and 16 and the top 64 Meg quadrants 14 and 17.Selecting between 32 Meg array blocks within any 128 Meg quadrant isaccomplished with a column address which is a function of part type andrefresh rate (e.g. 32 Meg uses <0:1> in the figure). Within any 32 Megarray block, the array is divided into eight blocks of four Meg each,and the blocks are organized into four pairs. For example, columnaddresses CA1011<0:3>select one of the four pair, and column addressCA_(—)7<0:1>selects between the four Meg blocks making up the pair.Columns within each four Meg block are accessed with an eight bitaddress. Those eight bits are represented by column addressesCA_(—)6<0:1>, CA45<0:3>, CA23<0:3>, CA01<0:3>, and CA_(—)8<0:1>. Columnaddress CA_(—)6<0:1> represents the most significant bit in the address,and column address CA_(—)8<0:1>represents the least significant bit inthe address.

[0411]FIG. 32B illustrates the row address mapping for a single 64 Megquadrant. Because row addresses are identical for each 64 Meg quadrant,row addressing will be described only with respect to a single 64 Megquadrant. Each 64 Meg quadrant is divided into two 32 Meg array blocks,and row address-RA_(—)13<0:1> selects between the two 32 Meg arrayblocks. Each 32 Meg array block is divided into sixteen blocks of twoMeg each, and those sixteen blocks are organized into four groups offour. Row addresses RA11<0:1>and 16 Meg select <0:1> together select oneof the four groups. 16 Meg select <0:1> is a function of part type andrefresh rate as shown in the table in the Figure. Within each group, rowaddresses RA910<0:3> select one of the two Meg blocks. Rows within eachtwo Meg block are accessed with a nine bit row address. Those nine bitsare represented by row addresses RA_(—)0<0:1>, RA12<0:3>, RA34<0:3>,RA56<0:3>, and RA78<0:3>. Row addresses RA78<0:3> represent the mostsignificant bits in the address, and row address RA_(—)0<0:1> representsthe least significant bit in the address.

[0412] Exemplary design specifications for the present preferredembodiment are as follows: TABLE 4 Product Overview Product 256 MbitDRAM Die Size 14.99 × 24.68 mm (590.5 × 971.6 Mil) w/scribe Package 16 ×25.55 mm (630 × 1006 mils) 62 pin SOJ/TSOPII (0.8 mm Lead Pitch) ShrinkFactor 0.24 MBit Size 0.6 μmF × .684 μmF Process .25 μm CMOS, 3-Poly,2-Metal, Rugged Poly container cell Async Speed 50/60 ns Active Power215 mA Standby Power 200 uA

[0413] TABLE 5 Features 3.3 volt supply internally regulated to 2.5volts Laser fuses and antifuse cell Redundancy 32 rows/32 Meg and 16cols/16 Meg Laser Fuse Redundancy 8 rows/32 Meg and 4 cols/16 MegAnti-Fuse Lead Over Chip Bonding (LOC) Separate power and ground pinsfor output buffers Fuse ID (laser and antifuse)

[0414] TABLE 6 Configurations Prime Part (Bond option) 32 Meg × 8 16 Meg× 16 8K refresh EDO 128 Meg Partial Die (Fuse Option) 8 Meg × 16 4Krefresh

[0415] VI. Bus Architecture

[0416] The power bussing scheme implemented in the present invention isbased upon central distribution of voltages from a central area 200illustrated in FIGS. 33A through 33C and 33D and E. The central area 200is where the pads are physically located on the chip 10. As seen inFIGS. 33D and E, a Vcc regulator 220 is centrally located within thepads area 200. As will be discussed hereinbelow in conjunction with FIG.35, the Vcc regulator 220 produces the array voltage Vcca and theperipheral voltage Vcc. A Vbb pump 280, discussed in detail hereinbelowin conjunction with FIG. 37, is located in the right portion of the padsarea 200 as seen in FIG. 33E. A Vccp pump, which is describedhereinbelow in conjunction with FIG. 39, is comprised of Vcc pumpcontrol 401, a first plurality of pump circuits 402, and a secondplurality of pump circuits 403. The Vccp pump produces a boosted versionof Vcc referred to as Vccp which is used for biasing the wordlines.Finally, a plurality of DVC2 generators 500, 501, 502, 503, 504, 505,506, and 507 are distributed throughout the central pads area 200. Oneof the DVC2 generators 500 is described in detail hereinbelow inconjunction with FIG. 41. The DVC2 generators 500-507 produce a voltagewhich is one-half of the peripheral voltage Vcc which is used forbiasing the digitlines and the cell plate.

[0417] As seen in FIGS. 33A, 33B, and 33C, the web 202 is constructed soas to emanate from the central pads area 200 to surround each of the 32Meg array blocks 40 and 47 illustrated in FIG. 33A, each of the arrayblocks 27, 33, 38, and 45 illustrated in FIG. 33B, and each of the arrayblocks 25 and 31 illustrated in FIG. 33C. For example, focusing upon thearray block 40 in FIG. 33A, it is seen that the web 202 is comprised ofa first plurality of conductors surrounding the array block 10 andcarrying the following voltages: mapAVC2, mapDVC2, mapVccp, Vss, Vbb,and Vcca. The voltages AVC2, DVC2, and Vccp may be switched as shown inFIGS. 3A and 3C such that those voltages are no longer delivered to thearray in the event the array is shut down. The web 202, comprised ofconductors carrying the foregoing voltages, surrounds each of the 32 Megarray blocks for efficient low resistance distribution.

[0418] Extending vertically into each 32 Meg array block at, forexample, nine locations, are conductors carrying the following voltages:mapvccp, Vcca, and Vss. Extending horizontally through the 32 Meg arrayblock at, for example, seventeen locations are conductors carrying thefollowing voltages: mapAVC2, Vss, Vcca, mapDVC2, and Vbb. Thus, not onlyare each of the array blocks ringed, the power bussing layout featuresfully gridded power distribution through a second plurality ofconductors for better IR and electromigration performance.

[0419]FIGS. 34A, 34B, and 34C illustrate the 71 pads and certain of theconductors connected to those pads. It is understood that the subjectmatter illustrated in FIGS. 34A, 34B, and 34C is located in the centralpads area 200 of FIGS. 33A through C and 33D and E. As seen in FIGS.34A, 34B, and 34C, the pads designated Vccq, which are pads 1, 5, 11,and 15 are connected to a Vccq conductor 204. Conductor 204 runsparallel to the central portion of the web 202 as best seen in FIG. 33Abut is not part of the web 202. The conductor 204 carries the powerneeded for the output buffers.

[0420] Pads 17, 32, and 53, which are designated Vccx, are connected toa Vccx conductor 206. Conductor 206 runs parallel to the central portionof the web 202 as best seen in FIG. 33B but is not part of the web. Pads59, 65, and 69, which are designated Vccq, are connected to a Vccqconductor 208. Conductor 208 runs parallel to the central portion of theweb 202 as best seen in FIG. 33C but is not part of the web 202. Above,and parallel to the conductors 204, 206, and 208, are conductors 210,211, and 212 for carrying the voltages Vcc, Vcca, and Vcc, respectively.The conductors 210, 211, 212 are part of the first plurality ofconductors forming the web 202.

[0421] A conductor 214, which provides a ground for the output buffers,is provided for connection to the pads designated Vssq which are pads 2,6, 12, and 16 as shown in FIG. 34A. Conductor 214 runs parallel to thecentral portion of the web 202 as best seen in FIG. 33A but is not partof the web. Another Vssq conductor 216 is provided for connection to thepads 56, 60, 66, and 70. Conductor 216 runs parallel to the centralportion of the web 202 as best seen in FIG. 33C but is not part of theweb 202. Finally, a conductor 218 is provided for connection to padsmarked Vss, which are pads 18, 33, and 54. The Vss conductor 218 alsoextends below and beyond the conductors 214 and 216 as illustrated inFIGS. 34A, 34B, and 34C. Conductor 218 is part of the first plurality ofconductors forming the web 202. Through that method of distribution,voltages impressed upon the pads are efficiently distributed to thevoltage supplies distributed throughout the central pads area 200 andthe external voltage and ground are made available for the data outputpad drivers.

[0422] VII. Voltage Supplies

[0423] The chip 10 of the present invention produces from the externallysupplied voltage Vccx all of the various voltages that are usedthroughout the chip 10. The voltage regulator 220 (FIG. 35) may be usedto produce the array voltage Vcca and the peripheral voltage Vcc. Thevoltage pump 280 (FIG. 37) may be used to produce a back bias voltageVbb for the die. The voltage pump 400 (FIG. 39) may be used to produce aboosted voltage Vccp needed for, inter alia, driving the word lines. TheDVC2 generators 500-507 (FIG. 41) may be used to produce a bias voltageDVC2 for biasing the digitlines and a voltage AVC2 (which is equal toDVC2) for the cellplate. The voltage regulator, Vbb pump, Vccp pump, andDVC2 generators, which may be collectively referred to as a powersupply, will each be described in detail.

[0424]FIG. 35 is a block diagram illustrating the voltage regulator 220which may be used to produce the peripheral voltage Vcc and arrayvoltage Vcca from the externally supplied voltage Vccx. As seen fromFIG. 33E, the voltage regulator 220 is located in the center of the padsarea 200 in what is referred to hereinbelow as the center logic (SeeSection VIII).

[0425] The process used to fabricate the chip 10 determines suchproperties as gate oxide thickness, field device characteristics, anddiffused junction properties. Each of those properties in turn effectsbreakdown voltages and leakage parameters which limit the maximumoperating voltage which a part produced by a particular process canreliably tolerate. For example, a 16 Meg DRAM built on a 0.35 μm CMOSprocess with 120 angstrom gate oxide can operate reliably with aninternal supply voltage not exceeding 3.6 volts. If that DRAM had tooperate in a 5 volt system, an internal voltage regulator would beneeded to convert the external 5 volt supply to an internal 3.3 voltsupply. For the same DRAM operating in a 3.3 volt system, an internalvoltage regulator would not be required. Although the actual operatingvoltage is determined by process considerations and reliability studies,the internal supply voltage is generally proportional to the minimumfeature size. The following table summarizes that relationship. TABLE 7Process Vcc Internal 0.45 μM 4.0 Volts 0.35 μM 3.3 Volts 0.25 μM 2.5Volts 0.20 μM 2.0 Volts

[0426] The circuit 220 is comprised of three major sections, anamplifier portion 222, a tri-region voltage reference circuit 224, whichproduces a reference voltage input to the amplifier portion 222, and acontrol circuit 226 which produces control signals input to theamplifier portion 222. Each will now be described in detail.

[0427] In FIG. 36A, the tri-region voltage reference circuit 224 isillustrated in detail. The tri-region voltage reference circuit 224 iscomprised of a current source 228. A current I1 flowing through aresistor 244 generates a voltage which is equal to the gate to sourcevoltage of a transistor 230. The drain to source voltage of anothertransistor 231 is equal to the gate to source voltage plus Vth. Thecurrent flowing through the transistor 231 is constrained by a currentmirror comprised of transistors 245, 246, 247, and 248 to be equal tothe current I1. In that manner, the current source 228 provides acurrent I1 to a circuit node 232. Current is drained from the circuitnode 232 by a trimmable, or programmable, “pseudo” diode stack 234. Thepseudo diode stack 234 is a plurality of transistors connected in serieswith their gate terminals connected to a common potential. The pseudodiode stack 234 is essentially a long channel FET which can beprogrammed or trimmed to provide the desired impedance.

[0428] Connected across each of the transistors in the pseudo diodestack 234 is a switching or trimming transistor from a stack 236 of suchtransistors. The gates of each of the switching transistors in the stack236 are connected to a reference potential through a closed fuse orother type of device which may be either opened or closed. Assumingfuses are used, half of the gates may be connected to a potential whichrenders the switching transistor conductive, thereby removing theassociated transistor from the stack 234 while the gates of theremaining transistors may be connected through fuses to a potentialwhich renders the switching transistor nonconductive, thereby leavingthe associated transistor in the stack 234. In that manner, fuses may beblown to either turn on or turn off a switching transistor to therebydecrease or increase, respectively, the impedance of the trimmable diodestack 234. In that manner, a reference signal (voltage) available at thecircuit node 232 can be precisely controlled. Such trimming is requireddue to process variations during fabrication.

[0429] The current source 228 together with the pseudo diode stack 234and switching transistors 236 form an active voltage reference circuitwhich produces the reference signal available at the circuit node 232that is responsive to the external voltage Vccx applied to the circuit224. Those components are considered to form an active voltage referencecircuit as contrasted with a resistor/trimmable pseudo diode stackcombination found in the prior art which passively produces a signal atnode 232. A bootstrap circuit 255 is also provided to “kickstart” thecurrent source 228.

[0430] The reference signal available at circuit node 232 is input to aunity gain amplifier 238. The output of the unity gain amplifier 238 isavailable at an output terminal 240 at which a regulated referencevoltage Vref is available. Use of an active voltage reference circuitfor producing the reference signal at circuit node 232 produces thedesired relationship between Vref and Vccx which is not available withprior art circuits at the voltage range. Additionally, by makingamplifier 238 a unity gain amplifier, common mode range and overallvoltage characteristics are improved.

[0431] The tri-region voltage reference circuit includes a pullup stage242 for pulling up the reference voltage available at output terminal240 so that the reference voltage substantially tracks the externalvoltage when the external voltage exceeds a predetermined value. Thepullup stage 242 is comprised of a plurality of diodes formed by pMOStransistors connected between the external voltage Vccx and the outputterminal 240. When the voltage Vccx exceeds the voltage at the terminal240 by the number of diode drops in the series connected diodescomprising the pullup stage 242, the pMOS diodes will be turned onclamping the voltage available at the output terminal 240 to Vccx minusthe voltage drop across the diode stack.

[0432] The voltage available at the output terminal 240 is input to theamplifier portion 222 of the voltage regulator 220 where it is amplifiedto produce both the array voltage Vcca and peripheral voltage Vcc aswill be described hereinbelow in conjunction with a description ofamplifier portion 222.

[0433] The relationship between the peripheral voltage Vcc and theexternally supplied voltage Vccx is illustrated in FIG. 36B. Thetri-region voltage reference circuit 224 is responsible for thoseportions of the curve occurring in region 2, corresponding to the“operating range” of the externally supplied voltage Vccx, and region 3,corresponding to the “burn-in range” of the externally supplied voltageVccx. The output of the tri-region voltage reference circuit 224 is notused to generate the peripheral voltage Vcc during region 1. Region 1 isimplemented by shorting the bus carrying the external voltage Vccx andthe bus carrying the peripheral voltage Vcc together though pMOS outputtransistors found in the power stage of each power amplifier as will bedescribed hereinbelow. The first region occurs during a powerup orpowerdown cycle in which the externally supplied voltage Vccx is below afirst predetermined value. In the first region, the peripheral voltageVcc is set equal to the externally supplied voltage Vccx to provide themaximum operating voltage allowable in the part. A maximum voltage isdesirable in region 1 to extend the DRAM's operating range and to ensuredata retention during low-voltage conditions.

[0434] After the first predetermined value for the externally suppliedvoltage Vccx has been reached, the buses carrying the voltages Vccx andVcc are no longer shorted together. After the first predetermined valuefor the externally supplied voltage Vccx is reached, the normaloperating range, region 2, illustrated in FIG. 36B is entered. In region2, the peripheral voltage Vcc flattens out and establishes a relativelyconstant supply voltage to the peripheral devices of the chip 10.Certain manufacturers strive to make region 2 absolutely flat, therebyeliminating any dependance on the externally supplied voltage Vccx. Amoderate amount of slope in region 2 is advantageous for characterizingperformance. It is important in the manufacturing environment that eachDRAM meet the advertized specifications with some margin for error. Asimple way to ensure such margins is to exceed the operating range by afixed amount during component testing. The voltage slope depicted inFIG. 36B allows that margin testing to occur by establishing a moderatedegree of dependance between the externally supplied voltage Vccx andthe peripheral voltage Vcc.

[0435] The third region illustrated in FIG. 36B is used for componentburn-in, and is entered whenever the externally supplied voltage Vccxexceeds a second predetermined value. That second predetermined value isset by the number of diodes in the diode stack comprising pullup stage242. During burn-in, both temperature and voltage are elevated above thenormal operating range to stress the DRAM and weed out infant failures.Again, if there were no relationship between the external voltage Vccxand the peripheral voltage Vcc, the internal voltage could not beelevated.

[0436] The characteristic of the peripheral voltage Vcc may besummarized as follows: the slope of the peripheral voltage Vcc issubstantially the same as the slope of the external voltage Vccx inregion 1 (up to the first predetermined value); the slope of theperipheral voltage Vcc is substantially less than the slope of theexternal voltage Vccx in region 2 (between the first predetermined valueand the second predetermined value); and the slope of the peripheralvoltage Vcc is greater than the slope of the external voltage Vccx inregion 3 (above the second predetermined value) because the signalavailable at output terminal 240, which substantially tracks theexternal voltage Vccx, is multiplied in an amplifier having a gaingreater than one.

[0437] The next section of the voltage regulator 220 is the controlcircuit 226. The control circuit 226 is comprised of a logic circuit 1250 illustrated in FIG. 36C, a Vccx 2v circuit 252 and a Vccx detectcircuit 253 illustrated in FIG. 36D, and a second logic circuit 258illustrated in FIG. 36E. Turning first to FIG. 36C, the logic circuit 1250 receives a number of input signals: SEL32M<0:7>, LLOW, EQ*, RL*,8KREF, ACT, DISABLEA, DISABLEA*, and PWRUP. The logic circuit 1 250 maybe comprised primarily of static CMOS logic gates and level translators.The logic gates are referenced to the peripheral voltage Vcc. The leveltranslators are necessary to drive the power stages, which arereferenced to the external voltage Vccx. A series of delay elements tunethe control circuit 226 relative to P-sense activation (ACT) and RAS*(RL*) timing. The purpose of the logic circuit 1 250 is: (i) to produce,from the aforementioned input signals, clamp signals (for both N and Ptype transistors) for shorting, in the power amplifiers, a voltage buscarrying the external voltage Vccx with a voltage bus supplying theperipheral voltage Vcc, (ii) to produce an enable signal (for both N andP type transistors) for enabling the power amplifiers, and (iii) toproduce a boost signal (for both N and P type transistors) for changingthe slew rate of the amplifiers. The particular combination of logicgates illustrated in FIG. 36C illustrates but one method of manipulatingthe aforementioned input signals to produce the previously listed outputsignals. The uses for the output signals will be described hereinbelowin conjunction with the amplifier portion 222. Other methods forproducing control signals are known. See, for example, U.S. Pat. No.5,373,227 entitled Control Circuit Responsive To Its Supply VoltageLevel and issued Dec. 13, 1994.

[0438]FIG. 36D illustrates the Vccx 2v circuit 252 and the Vccx detectcircuit 253. The circuit 252 receives the DISABLEA and DISABLEA* signalsand produces two reference signals, VSW and VTH. The circuit 253receives those signals and acts as a comparator to determine if thefirst predetermined value for Vccx (see FIG. 36B) has been reached.Circuit 253 may be implemented as a CMOS comparator. The circuit 253produces the signals PWRUP and PWRUP*. The PWRUP and PWRUP* signals areinput to a number of circuits, such as the logic circuit 1 250 and theamplifiers within the amplifier portion 222 as will be describedhereinbelow.

[0439]FIG. 36E illustrates the second logic circuit 258 which is thelast element of the control circuit 226. The second logic circuit 258produces the PUMPBOOST signal and the DISABLEA and DISABLEA* signalsused in other parts of the control circuit 226 from the following inputsignals: PWRDUP*, VccpON, VbbON, DISABLEA*, DISREG, and SVO. ThePUMPBOOST signal will be described in conjunction with the amplifierportion 222 whereas the other two signals output from the second logiccircuit 258 are, as mentioned, used both within the control circuit 226and in the amplifier portion 222.

[0440] Returning to FIG. 35, it is seen that the amplifier portion 222is comprised of a plurality of power amps 260, 261 a plurality of boostamps 262, and a standby amp 264 which are selectively operated toachieve better characteristics than those obtainable with a singleamplifier. The power amps 260 have greater than unity gain (e.g., 1.5×)which reduces the requirements of the reference voltage, Vref, andsmooth transitions such as between the powerup range and the operatingrange shown in FIG. 36B. Further, the power amps 260 may be controlledin groups (e.g., two groups of three each and a third group of twelve)rather than all on or all off at a time. Such controlled operationpermits the number of operational power amps 260 to be reduced whenpower demand is low. Such controlled operation also enables additionalamps to be activated, as needed, to achieve multiple refresh operations,e.g., firing two or more rows of the array at the same time. Asexplained further hereinbelow, the groups of power amplifiers haveadditional flexibility due to the ability to control individual poweramps in a group.

[0441] A further novel characteristic of the amplifier portion 222 is toinclude one or more boost amplifiers 262 that are specialized in thatthey operate only when voltage pumps fire.

[0442] A further component of the amplifier portion 222 is the standbyamplifier 264. The standby amplifier 264 allows for a further reductionin current consumption when the other amplifiers are not operating.Prior voltage regulators for DRAMs included a standby amplifier but notone in combination with the power amplifiers 260 and boost amplifiers262. In the present invention, the standby amplifier 264 does not needto be designed to provide a regulated supply for voltage pumps, which isaccomplished by the boost amplifiers 262, such that the standbyamplifier 264 may truly function as a standby amplifier.

[0443] The power amplifiers 260, boost amplifiers 262, and standbyamplifier 264 are similar in general structure but the power ampsoperate at a moderate bias current level (e.g., approximately 1 ma, orabout half of that required in the prior art) during memory arrayoperations, such as reading and writing. The boost amplifiers 262 aredesigned for a low bias such as about 300 μa, and may also have a lowerslew rate than the power amps because the boost amps operate only duringoperation of the voltage pumps which are described hereinbelow. Thestandby amplifier operates continuously at a very low bias of about 20μa. Through the use of multiple power amplifiers 260, boost amplifiers262, and the standby amplifier 244, minimization of operating currentfor each of the various operating conditions experienced by the DRAM isachieved.

[0444] Six of the amplifiers in the amplifier portion 222 may beconnected in parallel between the output of the tri-region voltagecircuit 224 and the bus 266 which carries the peripheral voltage Vcc andtwelve of the amplifiers in the amplifier portion 222 may be connectedin parallel between the output of the tri-region voltage circuit 224 andthe bus 267 which carries the array voltage Vcca. The power buses 266and 267 are isolated except for a twenty ohm resistor 269 that bridgesthe two buses together. Isolating the buses is important because itkeeps high current spikes that occur in the array from effecting theperipheral circuits. Failure to isolate buses 266 and 267 can result inspeed degradation for the DRAM because large current spikes in the arraymay cause voltage cratoring and a corresponding slowdown in logictransitions. With isolation, the peripheral voltage Vcc is almost immuneto array noise.

[0445] An electrical schematic illustrating one type of power amplifier260 is illustrated in FIG. 36F. To improve the slew rate, the poweramplifier 260 features a boost circuit 270 that raises the bias currentof a differential amplifier 272 to improve the slew rate during expectedperiods of large current spikes. Large spikes are normally associatedwith P-sense amp activation.

[0446] To reduce active current consumption, the boost circuit 270 isdisabled a short time after P-sense amp activation by the signal labeledpump BOOST. The power stages are enabled by the signal ENS* only whenRAS* is low and the part is active. When RAS* is high, all of the poweramplifiers 260 are disabled.

[0447] The signal labeled CLAMP* ensures that the pMOS output transistor274 is off whenever the amplifier is disabled to prevent unwantedcharging of the Vcc bus. When forced to ground, however, the signallabeled VPWRUP shorts the Vccx and Vcc buses together through a pMOSoutput transistor 274. The need for that function was described earlierin conjunction with the description of region 1 of FIG. 36B. Basically,the bus carrying Vccx and the bus carrying Vcc are shorted togetherwhenever the DRAM is operating in the powerup range of FIG. 36B. Thesignals CLAMP* and VPWRUP are mutually exclusive to prevent a shortcircuit between the external voltage Vccx and ground.

[0448] The ENS signal is supplied to the gate of a transistor switch 276whose conduction path is coupled at one end to the gate of one of thetransistors of the differential amplifier 272 through a resistor R1while the other end of the conduction path is tied to ground. A secondresistor R2 is connected between the gate of the aforementionedtransistor and the Vcc bus. The ratio of the resistors R1 and R2determines the closed loop gain of the circuit. As previously mentioned,the power amplifiers 260 have somewhat higher than unity gain.

[0449] An example of a boost amplifier 262 is illustrated in FIG. 36G.The boost amplifier 262 is very similar in construction and operation tothe power amplifier in that it has an output pMOS transistor capable ofshorting together the buses carrying Vccx and Vcc. The boost amplifiers262 also have a greater than unity gain as a result of the ratio betweenresistors R1 and R2. One difference between the boost amps 262 and thepower amps 260 is that that boost amps 262 are responsive to thePUMPBOOST signal so that the boost amps 262 are operational whenever thevoltage pumps are operational. Another difference is that the boostamplifiers 262 are designed to operate with a smaller bias current.

[0450] The standby amplifier 264 is illustrated in FIG. 36H. The standbyamplifier 264 is included to sustain the peripheral voltage Vcc wheneverthe DRAM is inactive, as determined by RAS*. The standby amplifier 264is similar in design to the other amplifiers in that it is built arounda differential pair, but is specifically designed for a very lowoperating current and a correspondingly low slew rate. Accordingly, thestandby amplifier 264 cannot sustain any type of active load.

[0451]FIG. 36I illustrates the details of one of the power amplifiers261 in the group of twelve power amplifiers 277 illustrated in FIG. 35.The power amplifiers 261 are of the same design as the boost amplifiers262 described hereinabove and illustrated in detail in FIG. 36G. Thepower amplifiers 261, however, receive different control signals thanthe boost amplifiers 262. For example, the power amplifiers 261 areresponsive to the CLAMPF* signal in a manner similar to the poweramplifiers 260. Furthermore, the power amplifiers 261 are responsive tothe VPWRUP and BOOSTF signals in a manner similar to the poweramplifiers 260. The functions of the CLAMPF*, VPWRUP, and BOOSTF signalsare described hereinabove with respect to the power amplifiers 260 andFIG. 36F.

[0452] The numbers of respective power amps 260, 261 and boost amps 262are matters of design choice according to the overall requirements ofthe DRAM. For example, a greater bandwidth is achieved by larger numbersof power amplifiers, which can be made relatively smaller if a largernumber are to be provided.

[0453] A further factor affecting the choice of the number of poweramplifiers has to do with the construction of the memory array. Asdescribed hereinabove, the memory array of the present invention isconstructed of eight 32 Meg array blocks. Each block can be shut down ifthe quantity of failures or the extent of the failures exceeds thearray's repair capability. That shutdown is both logical and physical.The physical shutdown includes removing power such as the voltages Vcc,DVC2, AVC2, and Vccp. It is often the case that the switches whichdisconnect power from the array block must be placed ahead of some ofthe decoupling capacitors 44 (seen in FIG. 3A) for that block. Thedecoupling capacitors 44 are provided to help maintain the voltageregulator's 220 stability. Reasons dictating the location of thedecoupling capacitors 44 include the desire to have some decouplingcapacitance proximate the array block because of possible current spikesin the array block and die geometry constraints. In the general case,the decoupling capacitance can be provided on both sides of the switchcontrolling an array block. When the total amount of decouplingcapacitance available on the die is reduced with each array block thatis disabled, there could be an adverse effect on voltage stability.Therefore, according to a further feature of the present invention, eacharray block has a corresponding power amplifier that is associatedtherewith and which is disabled whenever the array block is disabled.Disabling of a power amplifier 260 is accomplished by properlycontrolling the state of the ENS* signal produced by the eight pwr AmpDrive circuits seen in FIG. 36C. That compensates for the reduction indecoupling capacitance and maintains the desired voltage stability byremoving power amplifiers proportionately to the removal of decouplingcapacitance.

[0454] More specifically, in the preferred embodiment, the power amps260 are configured with a certain load capacitance and compensationnetwork such that their slew rate and voltage stability are consideredoptimum when there is about 0.25 nanofarads of decoupling capacitance inthe array block per power amplifier. In the disclosed embodiment, agroup of twelve power amplifiers (277 in FIG. 35), includes eight thatare respectively associated with each one of the eight array blocks andfour additional amplifiers that are not affected by the array switches.When a switch is opened that disables an array block and its associatesdecoupling capacitors, a signal is input to the control circuit 226 todisable the corresponding power amplifier to maintain the correct,optimal, relationship. In additional to maintaining voltage stability,that reduces unneeded current consumption. In general, more decouplingcapacitance is better for voltage stability and lower ripple but isworse for amplifier slew rate and hence an optimum is sought to bemaintained.

[0455] The next elements which comprise the voltage supplies provided onthe chip 10 are the voltage pumps, which include the voltage pump 280(FIG. 37) which may be used to produce the Voltage Vbb used to back biasthe die, and the voltage pump 400 (FIG. 39) which may be used to producethe Voltage Vccp which is a boosted voltage for the wordline drivers.Voltage pumps are commonly used to create voltages that are morepositive or more negative than available supply voltages. The Vbb pumpis typically built from pMOS transistors while the Vcc pump is builtprimarily from nMOS transistors. The exclusive use of nMOS transistorsor pMOS transistors in each pump is required to prevent latchup fromoccurring and prevent current injection into the mbit arrays. The use ofpMOS transistors is required in the Vbb pump because various activenodes will swing negative with respect to the substrate voltage, Vbb.Any n-diffusion regions connected to those active nodes would forwardbias and cause latchup and injection. Similar conditions mandate the useof nMOS transistors in the Vccp pump.

[0456] Turning to FIG. 37, the Vbb pump 280 is illustrated in blockdiagram form. As seen from FIG. 33E, the Vbb pump is located in theright portion of the pads area 200 in what is referred to hereinbelow asthe right logic (See Section X). The pump is constructed of two pumpcircuits 282, 283. An electrical schematic of one of the pump circuitsis illustrated in FIG. 38A. The pump circuit 283 is the same as thecircuit 282 and is therefore not illustrated.

[0457] In FIG. 38A, it is seen that the pump circuit 282 is responsiveto an oscillator signal OSC input at an input terminal thereof. Thecircuit 282 is comprised of an upper pump portion 285 and a lower pumpportion 286 which work in tandem to produce the output Voltage Vbb.Assume that the value of the oscillator signal OSC is such that theoutput of an inverter 290 available at a node 292 is high. A voltageavailable at a node 293 is clamped to ground by a pMOS transistor 294.The nodes 292 and 293 are separated by a capacitor 296. As theoscillator signal changes state such that the voltage available at thenode 292 begins to decrease, the transistor 294 will be turned off and aPMOS transistor 298 will become conductive so that the charge on thecapacitor 296 is made available to the bus carrying the voltage Vbb. Thelower pump portion 286 operates in substantially the same manner but isconstructed so that its output transistor 298′ is conductive when thetransistor 298 of upper pump portion 285 is nonconductive, and viceversa.

[0458] Returning to FIG. 37, the input to the pump circuits 282 and 283which controls their operation is the signal OSC which is generated by aVbb oscillator circuit 300. An electrical schematic of one type ofoscillator is illustrated in FIG. 38B. The oscillator circuit 300 usedin the voltage pump may be a CMOS ring oscillator of the typeillustrated in FIG. 38B. A unique feature of the oscillator circuit 300is the capability for multi-frequency operation permitted by theinclusion of mux circuits 302 which are connected to various differenttap points within the oscillator ring. The muxes, which are controlledby a signal labeled VBBOK*, enable higher frequency operation byreducing the number of inverter stages 304 comprising the ringoscillator. Typically, the oscillator circuit 300 is operated at ahigher frequency when the DRAM is in a powerup state, because the higherfrequency of operation will assist the Vbb pump to produce the requiredback bias voltage. The oscillator is enabled and disabled through asignal labeled OSCEN* which is produced by a Vbb regulator selectcircuit 306 as shown in FIG. 37. The oscillator may also include theconcepts disclosed in U.S. Pat. No. 5,519,360 entitled Ring OscillatorEnable Circuit With Immediate Shutdown, issued May 21, 1996,so that itcan be immediately shut down thereby reducing the amount of noise.

[0459] The Vbb regulator select circuit 306 is illustrated in detail inFIG. 38C. The circuit 306 receives the following input signals:DIFFVBBON, REG2VBBON, PWRDUP, DISVBB, and GNDVBB. The logic illustratedin FIG. 38C combines those signals to provide a signal labeled VBBREG*which is the same as the signal OSCEN* input to the oscillator 300. Aninverted version of that signal is also available as signal VBBON. Twoother signals are generated by the circuit 306, the signals labeledDIFFREGEN* and REG2EN*, which are used to select which of the tworegulator circuits 308 and 320 will be enabled.

[0460] Returning to FIG. 37, a Vbb differential regulator 2 circuit 308is provided. FIG. 38D illustrates an electrical schematic of the circuit308. The circuit 308, if enabled by the Vbb Regulator Select Circuit306, basically controls the operation of the Vbb pump circuits 282, 283albeit indirectly. The circuit 308 has a first portion 310 whichproduces the signal DIFFVBBON, that is input to the Vbb regulator selectcircuit 306, which produces the signal for running the oscillator 300,which drives the pump circuits 282, 283. The signal DIFFVBBON goes highwhenever the back bias voltage Vbb is more positive than minus 1 volt.

[0461] A second portion 312 of the circuit 308 produces the signalVBBOK* which is directly input to the oscillator 300. The signal VBBOK*speeds up the oscillator. The first circuit portion 310 and the secondcircuit portion 312 are the same circuit, and both operate asdifferential amplifiers. Basically, regardless of the specific circuitdesign, the Vbb differential regulator 2 circuit 308 should beconstructed using low-biased current sources and PMOS diodes totranslate the pump voltage Vbb to a normal voltage level. The readerseeking additional information concerning the Vbb differential regulator2 circuit 308 is directed to U.S. patent application Ser. No. 08/668,347entitled Differential Voltage Regulator, filed Jun. 26, 1996, andassigned to the same assignee as the present invention (Micron No.96-172).

[0462] Returning to FIG. 37, the last element of the Vbb pump is the VbbReg 2 circuit 320. An electrical schematic of the Vbb Reg 2 circuit 320is illustrated in FIG. 38E. The circuit 320 produces the REG2VBBONsignal input to the Vbb regulator select circuit 306. The input portionof the circuit 320 normalizes the input voltage. That normalized voltagelevel is then fed into a modified inverter stage having an adjustabletrip point. The trip point may be modified with feedback to providehysteresis for the circuit. Minimum and maximum operating voltages forthe Vbb pump 280 are controlled by the first inverter stage trip point,the hysteresis, and the pMOS diode voltages.

[0463] Two regulator 2 circuits (308 and 320) are provided for enablingthe selection of one of two control signals produced by circuitsimplementing different control philosophies. The Vbb differentialregulator 2 circuit 308 produces a control signal from a differentialamplifier stage. In contrast, the Vbb Reg 2 circuit 320 compares anormalized voltage to fixed trip points. Selection of one of the Vbbdifferential Reg 2 circuit 308 and Vbb Reg 2 circuit 320 may be madethrough a mask option. Depending upon the mask option selected, the vbbregulator circuit 306 produces one of the two signals DIFFREGEN* orREG2EN* for activating either the Vbb differential regulator 2 circuit308 or the Vbb regulator 2 circuit 320, respectively. The activatedregulator circuit then produces its control signal which is input to theVbb regulator select circuit 306 for production of the signal OSCEN* fordriving the Vbb oscillator circuit 300.

[0464] The other voltage pump used in the circuit 10 is the Vccp pump400 illustrated in FIG. 39. The Vccp pump 400 produces a boosted voltageVccp for, inter alia, the wordline drivers. The demand for the voltageVccp varies considerably in different refresh modes. For example, a 256Meg DRAM requires approximately 6.5 milliamps of current from the Vccppump 400 when operating in an 8K refresh mode. In contrast, the sameDRAM requires over 12.8 milliamps of current when operating in a 4Krefresh mode. Unfortunately, a Vccp pump that can provide adequatecurrent in 4K refresh mode is not suitable for use in an 8K refresh modebecause it will generate an unacceptable level of noise and excessiveVccp ripple with the relatively light load applied in 8K refresh mode.

[0465] The Vccp pump 400 of the present invention is comprised ofmultiple pump circuits, six (410, 411, 412, 413, 414, 415) beingillustrated in the embodiment shown in FIG. 39. All six pump circuits410-415 are used to generate Vccp voltage during 4K refresh mode.However, if all six pump circuits are operated during 8K refresh mode,an unacceptable level of noise and excessive Vccp ripple will begenerated because there will be an insufficient load on the pumps410-415. As a result, only a portion of the pump circuits 410-415 areused during 8K refresh mode.

[0466] The pump circuits 410-415 are divided into two groups, a primarygroup 422 comprising pump circuits 410-412, and a secondary group 423comprising pump circuits 413-415. The primary group 422 of pump circuits410-412 is always enabled by having their enable terminals tied to theperipheral voltage Vcc. The secondary group 423 of pump circuits413-415, however, are only enabled during 4K refresh mode by havingtheir enable terminals tied to a 4K signal. The 4K signal is produced inthe center logic as described herein below in conjunction with FIG. 59J.

[0467] In addition to the six pump circuits 410-415, the Vccp pump 400includes the control portion 401. As seen from FIGS. 33D and E, thecontrol portion 401 is found in the center logic (See Section VIII)while the pump circuits 410-415 are found in both the right and the leftlogic (See Section X).

[0468] All of the pump circuits 410-415 are driven by an OSC signalgenerated by an oscillator 424. The OSC signal acts as an additionalenable signal because it is required for the pump circuits 410-415 tooperate. The oscillator 424 may be controlled by either of tworegulators, a Vccp Reg. 3 circuit 426 or a differential regulatorcircuit 428. The regulators 426, 428 regulate Vccp by turning the pumpcircuits 410-415 on and off as needed to maintain Vccp at a desiredlevel. The regulators 426, 428 control the pump circuits 410-415indirectly by controlling the oscillator 424. Because only one of theregulators 426, 428 may control the oscillator 424, and thereby controlthe pump circuits 410-415, a selection between the two regulators 426,428 is made by a regulator select circuit 430. The selection may bemade, for example, by opening or closing connections within theregulator select circuit 430. Once a selection is made, the regulatorselect circuit 430 provides an enable signal to one of the regulators426, 428. The regulator select circuit 430 then enables the oscillator424 in response to signals received back from the enabled regulator 426or 428. FIG. 40A illustrates the details of one type of regulator selectcircuit 430.

[0469] The Vccp pump 400 also includes a burnin circuit 434. The burnincircuit 434 generates a signal BURNIN used by various components,including the pump circuits 410-415, to put components in a special“burnin mode” during component burnin tests. One type of burnin circuit434 is illustrated in detail in FIG. 40B.

[0470] The Vccp pump 400 further includes a pullup circuit 438. Thepullup circuit 438 connects the bus carrying Vccp to the bus carryingVcc whenever Vccp falls at least one Vth below Vcc. One type of pullupcircuit 438 is illustrated in detail in FIG. 40C.

[0471] The Vccp pump 400 also includes four clamp circuits 442, one ofwhich is seen in FIG. 40D. The clamp circuits 442 are usually enabledbut can be disabled in a Test mode. Vccp is normally higher than Vcc,usually by a little more than one Vth. However, if Vccp becomes toohigh, e.g., more than about three Vths above Vcc, it will be clamped toVcc to bring it back within acceptable limits. If Vccp becomes too low,e.g., more than about one Vth below Vcc, it will be clamped so as not tofall more than one Vth below Vcc by the clamp circuits 442. Thus, theclamp circuits 442 bracket Vccp to keep it no greater than three Vthsabove Vcc and no less than one Vth below Vcc.

[0472]FIG. 40E illustrates the details of one of the pump circuits 410.The pump circuits 410-415 are two-phase pump circuits, meaning that oneportion of the pump circuit pumps current when the OSC signal is highand another portion pumps current when the OSC signal is low. The pumpcircuits 410-415 are very similar in construction and operation to thepump circuits 282, 283 of the Vbb pump, except that nMOS transistors areused. The pump circuits 410-415 include a first latch 450 and a secondlatch 452 which pump current through capacitors 456, 456′ and drivelogic circuits 462, 462′. The logic circuit 462 provides a voltage to agate of a transistor 464. Transistor 464 conducts current to the Vccpbus when the OSC signal is low and transistor 464′ conducts current tothe Vccp bus when the OSC signal is high. The pump circuit 410 includesa Vccplim2 circuit 474 and a Vccplim3 circuit 476 which can be usedduring burnin mode to limit voltages on internal nodes of the pump. Thedetails of one type of Vccplim2 circuit 474 and the details of one typeof Vccplim3 circuit 476 are illustrated in FIGS. 40F and 40G,respectively.

[0473]FIG. 40H illustrates the details of the oscillator 424. Theoscillator 424 is a ring-type oscillator similar to the oscillator 300illustrated in FIG. 38B. The oscillator 424 has a variable a frequencyso that, for example, the pump circuits 410-415 may be operated at ahigher frequency during powerup to more quickly bring the Vccp bus toits operating voltage. The oscillator 424 includes a series of inverters478 which loops back on itself to form a ring. The time required for asignal to propagate through the inverters 478 determines the period ofthe signal OSC. Multiple frequency operation is implemented by theinclusion of several multiplexers 479 which receive signals from varioustap points in the chain of inverters 478. The multiplexers arecontrolled by a signal VPWRUP* and produce a higher frequency OSC signalby reducing the number of inverters 478 in the ring.

[0474]FIG. 40I illustrates the details of one type of Reg Vccp 3 circuit426 shown in FIG. 39. The circuit 426 may use several series connectedpMOS and nMOS diodes to “normalize” the voltage Vccp to the level ofVcc. In other words, several Vths are subtracted from Vccp by thediodes. The normalized voltage is used by transistors 480, 481, 482, and483 for generating an enable signal REG2VCCPON for the oscillator 424.If the normalized voltage is too high, a low value of the enable signalis generated, and if the normalized voltage is too low, a high value ofthe enable signal is generated.

[0475]FIG. 40J illustrates the details of the differential regulatorcircuit 428 shown in FIG. 39. The differential regulator circuit 428generates an enable signal DIFFVCCPON by comparing Vccp with a referencevoltage in a differential amplifier 486. When Vccp is below thereference voltage, a high value of the enable signal is generated toenable the oscillator 424. When Vcc is above the reference voltage, alow value of the enable signal is generated to disable the oscillator424. A similar differential regulator circuit is disclosed in U.S.patent application Ser. No. 08/521,563 entitled Improved Voltage RegularCircuit, filed Aug. 30, 1995, and assigned to the same assignee as thepresent invention (Micron No. 94-088).

[0476] The last of the voltage supplies on the chip 10 are the DVC2generators one of which, generator 500, is illustrated in FIG. 41. FIG.41 is a block diagram of one of the DVC2 generators 500 located in theright and left logic (See Section X). The DVC2 generator 500 produces avoltage of one half of Vcc, known as DVC2, for biasing the memorycapacitor cellplates. A related voltage, AVC2, which has the same valueas DVC2, is used for biasing the digitlines between array accesses. TheDVC2 generator 500 includes a voltage generator 510 for producing thevoltage DVC2 and an enable 1 circuit 512 for enabling and disabling thevoltage generator 510. A stability sensor 514 receives the output fromthe voltage generator 510 and produces an output signal indicative ofwhether the voltage DVC2 is stable.

[0477] The stability sensor 514 includes an enable 2 circuit 515 whichgenerates enable signals for the stability sensor 514. The stabilitysensor 514 includes a voltage detection circuit 516 for producing asignal indicative of whether the voltage level of the voltage DVC2 iswithin a first predetermined range. A pullup current monitor 518produces a signal indicative of whether a pullup current is stable. Apulldown current monitor 520 produces a signal indicative of whether apulldown current is stable. An overcurrent monitor 522 produces a signalindicative of whether the pullup current is above a predetermined value,suggesting short circuits within the array.

[0478] An output logic circuit 524 receives the output signals from thevoltage detection circuit 516, the pullup current monitor 518, and thepulldown current monitor 520, and produces an output signal indicativeof whether the voltage DVC2 is stable. The output of the overcurrentmonitor 522 is not input to the output logic 524 because overcurrent isnot a measure of the stability of the voltage DVC2. Instead, theovercurrent output signal may be used during testing of the DRAM todiagnose defective array blocks. Furthermore, the output of theovercurrent monitor 522 may be latched at the end of powerup and used bythe DRAM for self-diagnosis to determine whether an excessive currentsituation exists and whether a partial array shutdown is required.

[0479] Although the stability sensor 514 will be described as being usedwith the voltage generator 510 producing the voltage DVC2, the stabilitysensor 514 may be used with any power source, either on an integratedcircuit or constructed of discrete components. Furthermore, thestability sensor 514 will be described as including the voltagedetection circuit 516, the pullup current monitor 518, the overcurrentmonitor 522, and the pulldown current monitor 520. Any of thosecomponents, however, may be used individually or in other combinationsto provide an indication of the stability of a voltage generator.

[0480]FIG. 42A illustrates the details of the voltage generator 510shown in FIG. 41. The voltage generator 510 is enabled by a signalDVC2EN* received from a powerup sequence circuit described below inSection XI, and signals ENABLE and ENABLE* received from the enable 1circuit 512. The voltage generator 510 generates the voltage DVC2 whichis available at a node 530 by varying the conductivity of transistors532 and 534 connecting node 530 to Vcc and to ground, respectively.Current flowing from Vcc through transistor 532 to node 530 is “pullup”current because it raises the voltage at node 530. Current flowing fromnode 530 through transistor 534 to ground is “pulldown” current becauseit lowers the voltage of node 530. Pullup current and pulldown currentare controlled by controlling the gate voltage, and thereby theconductivity, of transistors 532 and 534, respectively. Feedback isprovided from node 530 to the gates of a series of pMOS transistors 536and the gates of a series of nMOS transistors 538. The transistors 536control the resistance of the path from the voltage vcc to the gate oftransistor 532. Two nMOS transistors 540 and 542 control the resistanceof the path away from the gate of transistor 532. The nMOS transistors538 control the resistance of the path from the gate of transistor 534to ground. A pMOS transistor 548 controls the resistance of the path ofthe gate of transistor 534 to Vcc. A series of capacitors 550 and 552connect the gate of transistor 532 to Vcc and to ground, respectively,thereby smoothing transitions in the gate voltage. Likewise, capacitors554 and 556 connect the gate of transistor 534 to Vcc and to ground,respectively.

[0481] In operation, the voltage DVC2 is held steady under varying loadsby controlling transistors 532 and 534 in response to feedback signals.If DVC2 is too high, pMOS transistors 536 begin to turn off therebylowering the gate voltage of transistor 532 and decreasing the pullupcurrent. At the same time, nMOS transistors 538 begin to turn on therebydecreasing the gate voltage and resistance of transistor 534 andincreasing the pulldown current. The combination of decreased pullupcurrent and increased pulldown current decreases the value of the DVC2voltage. Conversely, if DVC2 is too low, transistors 536 begin to turnon thereby increasing the gate voltage of transistor 532 and increasingthe pullup current. In addition, transistors 538 begin to turn offthereby increasing the gate voltage of transistor 534 and decreasing thepulldown current. The combination of increased pullup current anddecreased pulldown current raises the voltage of DVC2. Related circuitryis disclosed in U.S. Pat. No. 5,212,440 entitled Quick Response CMOSVoltage Reference Circuit issued May 18, 1993.

[0482]FIG. 42B illustrates the details of one type of enable 1 circuit512 shown in FIG. 41. The enable 1 circuit 512 generates the signalsENABLE and ENABLE* for enabling the voltage generator 510.

[0483]FIG. 42C illustrates the details of one type of enable 2 circuit515 shown in FIG. 41. The enable 2 circuit 515 generates signalsSENSEON, SENSEONB, SENSEON*, and SENSEONB*. Those signals are used toenable the voltage detection circuit 516, the pullup current monitor518, the overcurrent monitor 522, and the pulldown current monitor 520.

[0484]FIG. 42D illustrates the details of one type of voltage detectioncircuit 516 shown in FIG. 41. The voltage detection circuit 516 isenabled by signals SENSEON and SENSEON*. The voltage detection circuit516 receives the voltage DVC2 from the voltage generator 510 andproduces signals VOLTOK1 and VOLTOK2 indicative of whether the voltageDVC2 is within a predetermined range of voltages. The predeterminedrange is defined by ground plus the turn-on voltage of an NMOStransistor 560, and Vcc minus the turn-on voltage of a pMOS transistor562. The range may be adjusted by adjusting the turn-on voltages of thetransistors 560 and 562. The voltage DVC2 is connected to the gate ofthe nMOS transistor 560 and the gate of the pMOS transistor 562, andonly when the voltage DVC2 is within the predetermined range are both ofthe transistors 560 and 562 turned on and both of the signals VOLTOK1and VOLTOK2 at a high logic value. If the voltage DVC2 is too high,transistor 560 will be turned on but transistor 562 will be turned off,so that signal VOLTOK1 will be high but signal VOLTOK2 will be low.Likewise, if the voltage DVC2 is too low, transistor 560 will be turnedoff but transistor 562 will be turned on, so that signal VOLTOK1 will below and signal VOLTOK2 will be high.

[0485] More particularly, a resistor 564 allows current to trickle fromVcc to the input terminal of an inverter 566. When transistor 560 isturned off, the current coming through resistor 564 creates a high logicstate at the input terminal of the inverter 566. When transistor 560 isturned on, current flows through transistor 560 and the input terminalof the inverter 566 is pulled to a low logic state. Likewise, a resistor568 allows current to drain from the input terminal of an inverter 570,resulting in a low logic state. When transistor 562 is turned off, thelow logic state is-undisturbed at the input terminal of inverter 570.When transistor 562 is turned on, however, current flows throughtransistor 562 and into the input terminal of the inverter 570, and ahigh logic state exists at the input terminal of inverter 570.

[0486]FIG. 42E illustrates the details of one type of pullup currentmonitor 518 shown in FIG. 41. The pullup current monitor 518 is enabledby signals SENSEONB, SENSEONB*, and ENABLE*, is responsive to the PULLUPcurrent and the voltage DVC2, and produces signals PULLUPOK1 andPULLUPOK2 indicative of whether the pullup current is stable. The pullupcurrent monitor 518 includes several current sources in the form oftransistors 582, 583, 584, and 585. The current sources 582-585 areresponsive to the PULLUP current such that each transistor sources acurrent indicative of the present pullup current in the voltagegenerator 510. The pullup current monitor 518 also includes severalcurrent sinks in the form of transistors 588, 589, and 590. The currentsink 588 sinks a current indicative of the present pullup current. Thecurrent sinks 589-590 each sink a current indicative of a past pullupcurrent. A time delay between the past pullup current and the presentpullup current is defined by an RC time constant created by a resistor594 and a capacitor 596. The charge on the capacitor 596 is indicativeof the past pullup current and changes when current flows into or out ofthe capacitor 596 through-the resistor 594. Current flows into capacitor596 when the source current from transistor 582 is greater than the sinkcurrent flowing through transistor 588. Conversely, current flows out ofcapacitor 596 when the source current from transistor 582 is less thanthe sink current through transistor 588. A delay in the charging and thedischarging of the capacitor 596 is caused by the RC time constant andcan be adjusted to obtain a desired delay between the current sinks589-590 and the current sources 582-585. Transistors 589-590 have gatesconnected to capacitor 596 such that they each sink a current indicativeof the past pullup current.

[0487] As seen in FIG. 42E, transistor 582 is connected in series withtransistor 588, transistor 583 is connected in series with transistor589, and transistor 585 is connected in series with transistor 590. Inoperation, transistor 588 acts to control the current input to thecapacitor 596. When the source current exceeds the sink current,transistor 582 is generating more current than transistor 588 issinking. As a result, the additional source current flows throughresistor 594 and charges capacitor 596. If the source current is lessthan the sink current, then transistor 588 is sinking more current thantransistor 582 is sourcing and the additional sink current flows fromthe capacitor 596 through the resistor 594 and through transistor 588,thereby decreasing the charge on capacitor 596.

[0488] A resistor 600, current source 583, and current sink 589 form apositive differential current circuit for determining whether thepresent pullup current is greater than the past pullup current. When thesource current through transistor 583 is greater than the sink currentthrough transistor 589, the additional source current flows throughresistor 600 to ground. That current creates a positive voltage acrossresistor 600, raising the voltage at an input terminal of an inverter602. When the voltage at the input terminal of the inverter 602 becomesa high logic value, the inverter 602 will change the output signalPULLUPOK1 to a low logic value indicating an increase in the pullupcurrent. When the source current is less than or equal to the sinkcurrent, the voltage across resistor 600 is zero or negative, and doesnot affect the signal PULLUPOK1.

[0489] Similarly, a resistor 606, current source 585, and current sink590 form a negative current differential circuit for determining whetherthe present pullup current is less than the past pullup current. Whenthe sink current through transistor 590 is greater than the sourcecurrent through transistor 585, the additional sink current flows fromVcc through resistor 606 and into transistor 590. As a result, a voltageat an input terminal of an inverter 608 is lowered. When the voltage atthe input terminal of the inverter 608 becomes a low logic value, thesignal PULLUPOK2 will change to a low logic value as a result of theseries connection of inverter 608 with an inverter 609 therebyindicating that the pullup current has decreased. However, when the sinkcurrent through transistor 590 is equal to or less than the sourcecurrent through transistor 585, additional current builds up at theinput terminal of inverter 608, causing the voltage at the inputterminal of inventor 608 to remain at a high logic value, therebymaintaining a high logic value for the PULLUPOK2 signal.

[0490] The pullup current monitor 518 also includes the overcurrentmonitor 522. The overcurrent monitor 522 includes current source 584 andgenerates a signal DVC2HIC indicative of whether the pullup current isexcessive. The source current from transistor 584 flows into a resistor514. Resister 514 converts the current into a voltage that is monitoredby an inverter 616. As long as the source current is not too high, theinput terminal of inverter 616 remains at a low logic state. If,however, the source current becomes excessive, the input terminal ofinverter 616 changes to a high logic state and causes signal DVC2HIC toassume a high logic state, as a result of the series connection of theinverter 616 with an inverter 617, indicating an overcurrent situation.The amount of current required to trigger the overcurrent monitor isdefined by the input voltage at which the inverter 616 changes statesdivided by the resistance of resistor 514.

[0491] The pulldown current monitor 520 illustrated in FIG. 42Ffunctions in an analogous manner to the pullup current monitor 518. Thepulldown current monitor 520 includes current sinking transistor 620-622for sinking a current indicative of the present pulldown current in thevoltage generator 510. The pulldown current monitor 520 also includescurrent sourcing transistor 626-628. Transistor 626 generates a sourcecurrent indicative of the present pulldown current and transistors 627and 628 generate a source current indicative of a past pulldown current.The time difference between the present pulldown current and the pastpulldown current is defined by an RC time constant formed from aresistor 630 and a capacitor 632. Pulldown current monitor 520 alsoincludes a resistor 636 forming part of a positive differential currentcircuit for producing signal PULLDOWNOK1 and a resistor 638 forming partof a negative differential current circuit for producing signalPULLDOWNOK2. The pulldown current monitor 520, however, does not includea circuit analogous to the overcurrent monitor 522.

[0492]FIG. 42G illustrates the details of the output logic 524 shown inFIG. 41. The output logic 524 is enabled by signal ENABLE and receivessignals VOLTOK1 and VOLTOK2 from the voltage detection circuit 516,PULLUPOK1 and PULLUPOK2 from the pullup current monitor 518, andPULLDOWNOK1 and PULLDOWNOK2 from the pulldown current monitor 520. Ifthe output logic 524 is enabled, and if all the input signals indicatethat the voltage generator 510 is stable, the output logic 524 willgenerate a signal DVC2OK*, indicating that the DVC2 voltage is stable.That completes the description of the voltage supplies.

[0493] VIII. Center Logic

[0494] The center logic 23 illustrated in FIG. 2 is illustrated in blockdiagram from in FIG. 43. The center logic is responsible for performinga number of functions including processing of the row address strobesignals in a RAS chain circuit 650, processing of column address strobesignals in control logic 651, row address predecoding in row addressblock 652, and column address predecoding in block 654. The center logic23 also contains test mode logic 656, option logic 658, a “spares”circuit 660, and a misc. signal input circuit 662. The control portion401 of the Vccp pump 400 (see FIG. 39) and the voltage regulator 220(see FIG. 35) are located in the center logic. Completing thedescription of the center logic 23 illustrated in FIG. 43, a power upsequence circuit 1348 of the type illustrated in FIG. 100 is alsoprovided. Each of the blocks 650, 651, 652, 654, 656, 658, 660 and 662illustrated in FIG. 43 will now be described. The voltage regulator 220and the control portion 401 of the Vccp pump 400 have already beendescribed hereinabove in Section VII; the power up sequence circuit 1348is described hereinbelow in Section XI.

[0495] The RAS chain circuit 650 is illustrated in block diagram form inFIG. 44. The purpose of the RAS chain circuit 650 is to provide read andwrite control signals for the circuit 10. Beginning in the upper lefthand corner of FIG. 44, a RAS D generator 665 is provided. The purposeof the generator 665 is to simulate the time needed for the addressbuffers to set up. A signal RASD is produced by the generator 665 inresponse to that simulation. An electrical schematic of one type of RASD generator 665 is illustrated in FIG. 45A.

[0496] The next circuit in the RAS chain circuit 650 is the enable phasecircuit 670. The purpose of the circuit 670 is to generate phase signalsENPH, ENPH* used for timing purposes. An electric schematic of one typeof circuit 670 is illustrated in FIG. 45B.

[0497] An ra enable circuit 675 is provided to generate row addresslatch signals RAL and row address enable signals RAEN*. Those signalsare input to an equilibration circuit 700 and an isolation circuit 705,the purpose of which will be described hereinbelow. An electricschematic illustrating one type of circuit 675 is illustrated in FIG.45C.

[0498] The RAS chain circuit 650 includes a WL tracking circuit 680 thepurpose of which is to approximate how long it takes a wordline to fire.An electrical schematic of one type of tracking circuit 680 isillustrated in FIG. 45D. The tracking circuit illustrated in FIG. 45D iscomprised of a first portion 681 which estimates the time needed for therow encoders to power up, a second portion 682 which estimates the timerequired for the array to power up (shown schematically in theenlargement), and a third portion 683 which provides additional delaybefore the signal WLTON is produced. The signal WLTON is used forwordline tracking.

[0499] A sense amps enable circuit 685 is provided which producessignals ENSA, ENSA* for firing the N-sense amplifiers and signals EPSA,EPSA* for firing the P-sense amplifiers. An electrical schematic of onetype of sense amps enable circuit 685 is illustrated in FIG. 45E.

[0500] A RAS lockout circuit 690 is provided for generating a signalRASLK* which is used elsewhere in the logic for lockout purposes. Anelectric schematic of one type of RAS lockout circuit 690 is illustratedin FIG. 45F.

[0501] An enable column circuit 695 is provided to produce the signalsECOL, ECOL* which are used to enable the column address circuitry. Anelectrical schematic of one type of enable column circuit 695 isillustrated in FIG. 45G.

[0502] An equilibration circuit 700 and isolation circuit 705 eachreceive the signals RAEN*, RAEND which are used to produce the EQ*signal and ISO* signal, respectively. The EQ* signal is used to controlthe equilibration process while the ISO* signal controls the isolationof the array. An electrical schematic of one type of circuit which maybe used for the equilibration circuit 700 is illustrated in FIG. 45Hwhile an electrical schematic of one type of circuit which may be usedfor the isolation circuit 705 is illustrated in FIG. 45I.

[0503] A read/write control circuit 710 is provided for producing thesignals CAL* and RWL. The purpose of the S circuit 710 is to latch thecolumn address buffers when the correct combination of CAS*, RAS*, andWE* are provided at the input thereto. An electrical schematic of onetype of circuit which may be used for the read/write control circuit 710is illustrated in FIG. 45J.

[0504] A write time out circuit 715 is provided to control the writefunction. That control is implemented through the production of a signalWRTLOCK* which is input to the read/write control circuit 710 forcontrol purposes. An electrical schematic of one type of write time outcircuit 715 is illustrated in FIG. 45K.

[0505] A plurality of data in latches 720 and 725 are provided forlatching data. An electrical schematic of one type of latch circuitwhich may be used for data in latch 720 is illustrated in FIG. 45L whilean electrical schematic of one type of latch circuit which may be usedfor the data in latch 725 is illustrated in FIG. 45M. The latch circuits720 and 725 may, in fact, be identical with only the signals inputthereto changing.

[0506] A stop equilibration circuit 730 is provided to generate a signalSTOPEQ* for the purposes of ending the equilibration process. Anelectrical schematic of one type of stop equilibration circuit 730 whichmay be used is illustrated in FIG. 45N.

[0507] Completing the description of the RAS chain circuit 650, a CAS LRAS H circuit 735 and a RAS-RASB circuit 740 are provided to monitor thestatus of the CAS and RAS signals for producing output signals usedelsewhere in the logic, and ultimately for controlling the amount ofpower generated by the voltage regulators. An electrical schematic ofone type of CAS L RAS H circuit 735 is illustrated in FIG. 450 while anelectrical schematic of one type of RAS-RAS B circuit 740 is illustratedin FIG. 45P.

[0508] The control logic 651 illustrated in FIG. 43 is illustrated inblock diagram form in FIG. 46. The control logic 651 includes a RASbuffer 745. The RAS buffer produces two output signals PROW* which isfor powering up the row address buffer and a signal RAS* which startsthe RAS chain circuit 650. An electrical schematic of one type of RASbuffer which may be used for the buffer 745 is illustrated in FIG. 47A.

[0509] A fuse pulse generator 750 is provided which is responsive to thepowered up signal, produced by the powerup sequence circuit describedhereinbelow, and the RAS* signal. The fuse pulse generator 750 producesa number of pulses which effectively prompt the circuit 10 to determinethe status of various bond options and fuses. An electrical schematic ofone type of fuse pulse generator 750 is illustrated in FIG. 47B.

[0510] An output enable buffer 755 is responsive to a number of inputsignals for producing an output enable OE signal. An electricalschematic of one type of output enable buffer which may be used for theoutput enable buffer 755 is illustrated in FIG. 47C.

[0511] The next two circuits, a CAS buffer 760 and a dual CAS buffer765, are responsive to various input signals related to the CAS signalto produce output signals input to a QED logic circuit 775. In an ×16part, CAS H refers to the eight most significant bits of the data whileCAS L refers to the eight least significant bits of the data. Anelectrical schematic illustrating one type of CAS buffer which may beused for the CAS buffer 760 is illustrated in FIG. 47D while 47E is anelectrical schematic of one type of dual CAS buffer which may be usedfor the dual CAS buffer 765.

[0512] A write enable buffer 770 produces a write enable signal WE* anda signal PWE* which are input to the QED logic circuit 775. Anelectrical schematic of one type of circuit which may be used for thewrite enable buffer 770 is illustrated in FIG. 47F.

[0513] The QED logic circuit 775 is responsive to a number of inputsignals illustrated in both FIG. 46 and FIG. 47G. The QED logic circuit775 is responsible for producing the control signals QEDL, responsiblefor the low byte, and QEDH, responsible for the high byte. The controlsignals QEDL and QEDH are ultimately responsible for controlling thetransfer of data. The electrical schematic illustrated in FIG. 47Gillustrates one type of QED logic circuit which may be used for the QEDlogic circuit 775.

[0514] A data out latch 780 is provided to hold the data until the CASsignal goes low and new data is latched. An electrical schematic for onetype of data latch which may be used as the data out latch 780 isillustrated in FIG. 47H.

[0515] A row fuse precharge circuit 785 produces signals which are inputto row fuse blocks, discussed hereinbelow, for initiating the process ofdetermining if there is a match between a row address and a redundantrow address. An electrical schematic of one type of circuit which may beused for the row fuse precharge circuit 785 is illustrated in FIG. 47I.

[0516] A CBR circuit 790 is provided for determining when there is anoccurrence of CAS before RAS. An electrical schematic of one type ofcircuit suitable for the CBR circuit 790 is illustrated in FIG. 47J.

[0517] A pcol circuit 800 is provided which is responsive to the inputsignals RAS*, WCBR, CBR, and RAEN* for producing the signals PCOL WCBR*,PCOL*, and PCOL. An electrical schematic of one type of circuit whichmay be used for the p col circuit 800 is illustrated in FIG. 47K. Thesignal PCOL WCBR* is input to the column predecode enable circuits toenable the column predecoders.

[0518] Finally, write enable circuits 805 and 810 are provided which aresubstantially identical in construction and 5 operation. An electricalschematic of one type of write enable circuit which may be used for thecircuit 805 is illustrated in FIG. 47L while an example of a writeenable circuit which may be used for the circuit 810 is illustrated inFIG. 47M.

[0519] The row address block 652 of FIG. 43 is illustrated in blockdiagram form in FIGS. 48A and B. In FIGS. 48A and B a number of rowaddress buffers 820 through 833 are illustrated. Each of the row addressbuffers 820 through 833 is responsive to a different bit of the rowaddress information. The row address buffers are also responsive to arow address enable circuit 835 while the first row address buffer 820 isresponsive to a clock 837. The row address block 652 also includes a rowaddress predecoder 840 comprised of a 2 inv driver 842, an all row Pdecode row driver 844, and a plurality of NANDP decoders 846 through850. The row address block 652 also includes a 4 k8 k log circuit 852and an 8 k16 k log circuit 854.

[0520] An electrical schematic of the row address buffer 820 as well asthe row address enable circuit 835 and clock 837 is illustrated in FIG.49A. FIGS. 49B and 49C illustrate the wiring between the row addressbuffers 820 through 833. The electrical schematics illustrated in FIG.49A and the wiring diagrams illustrated in FIGS. 49B and C are oneimplementation of the required functionality.

[0521] Turning to FIG. 50A, an example of a 2 inv driver 842 isillustrated. Also illustrated is an example of one type of an all row Pdecode row address driver 844 and an exemplary circuit for the NAND Pdecoders 846. The inputs and outputs for the NAND P decoders 847, 848,and 849 are illustrated in FIG. 50B. It is to be understood that theNAND P decoders 847, 848, and 849 illustrated in FIG. 50B may take theform of the NAND P decoder 846 illustrated in FIG. 50A. Finally, theNAND P decoder 850 and the log circuits 852 and 854 are illustrated indetail in FIG. 50C.

[0522]FIGS. 51A and 51B illustrate in block diagram form the columnaddress block 654 illustrated in FIG. 43. The column address block 654is comprised of a plurality of column address buffers 860 through 872which are each responsive to a bit of the column address information.The column address buffers 860 through 868 are also responsive to a pcoladdress 1 circuit 874. The column address buffer 869 is responsive to apcol address circuit 876. Similarly, the column address buffers 870,871, 872 are each responsive to a pcol address 10, address 11, andaddress 12 circuits 878, 880, and 882, respectively.

[0523] The column address block 654 also includes a column predecodeportion 884 which includes a column P decoder enable circuit 886 and aplurality of encode P decoders 888 through 893. The decoder 893 is alsoresponsive to a mux 895.

[0524] Completing the description of the column address block 654illustrated in FIG. 51B, two select circuits, a 16 meg select circuit897 and a 32 meg select circuit 898 are provided to produce controlsignals which dictate the functions of the various addresses. Anequilibration driver 900 is responsive to a plurality of ATD 4ANDcircuits 902, 903, and 904.

[0525]FIGS. 52A, 52B, and 52C illustrate the column address buffers 860through 872 with the column address buffer 860 and the column addressbuffer 872 being illustrated as electrical schematics. Also illustratedas electrical schematics are the pcol address 1 circuit 874 and the pcoladdress 9 circuit 876. The address circuits 878, 880, and 882 areillustrated as electrical schematics in FIG. 52D. The reader shouldunderstand that the electrical schematics and wiring configurationillustrated in FIGS. 52A through 52D illustrate but one example forimplementing and interconnecting the column address buffers.

[0526] The predecoder portion 884 of the column address block 654 isillustrated as an electrical schematic and wiring diagram in FIG. 53.One of the encode P decoders 888 is illustrated as an electricalschematic as are the column P decoder enable circuit 886 and the mux895. The reader should understand that the electrical schematic andwiring configuration illustrated in FIG. 53 is but one implementationfor the predecoder portion 884.

[0527] An electrical schematic which may be used to implement the 16 megselect circuit 897 is illustrated in FIG. 54A. An electrical schematicwhich may be used to implement the 32 meg select circuit 898 isillustrated in FIG. 54B. The select circuits 897 and 898 determine thesignificance of the address information.

[0528] Finally, the equilibration driver 900 and associated circuits902, 903, 904 are illustrated as an electrical schematic in FIG. 55. Theequilibration driver 900 produces the signals which are used toequilibrate the sense amps and IO lines. The reader should understandthat the electrical schematic illustrated in FIG. 55 is but one way toimplement the equilibration driver 900.

[0529] The test mode logic 656 illustrated in FIG. 43 is illustrated asa block diagram in FIG. 56. In FIG. 56, the test mode logic 656 iscomprised of the following circuits:

[0530] a test mode reset circuit 910 shown in detail in FIG. 57A;

[0531] a test mode enable latch 912 shown in detail in FIG. 57B;

[0532] a test option logic circuit 914 shown in detail in FIG. 57C;

[0533] a supervolt circuit 916 shown in detail in FIG. 57D;

[0534] a test mode decode circuit 918 shown in detail in FIG. 57E;

[0535] a plurality of SV test mode decode 2 circuits 920 and a pluralityof associated output buses 921 shown in detail in FIG. 57F;

[0536] an optprog driver circuit 922 shown in detail in FIG. 57F;

[0537] a red test circuit 923 shown in detail in FIG. 57G;

[0538] a Vccp clamp shift circuit 924 shown in detail in FIG. 57I;

[0539] a DVC2 up/down circuit 925 shown in detail in FIG. 57I;

[0540] a DVC2 OFF circuit 926 shown in detail in FIG. 57J;

[0541] a pass Vcc circuit 927 shown in detail in FIG. 57K;

[0542] a TTLSV circuit 928 shown in detail in FIG. 57L; and

[0543] a disred circuit 929 shown in detail in FIG. 57M.

[0544] An electrical schematic of one type of test mode reset circuitwhich may be used for the reset circuit 910 is illustrated in FIG. 57A.If a test mode is to be reset, test mode reset circuit 910 provides theSVTMRESET signal to the SV test mode decode 2 circuits 920 of FIG. 57Fand the TMRESET signal to the test mode decode circuit 918 of FIG. 57E.

[0545] An example of a test mode enable latch 912 is illustrated in FIG.57B. In the present preferred embodiment of the invention, addresseshave been divided into two categories: for the low set of addresses,signal SVTMLATCHL is used while the signal SVTMLATCHH is used for thehigh set of addresses. The signals SVTMLATCHL and SVTMLATCHH aremutually exclusive. The signal TMLATCH is supplied to the test modedecode circuit 918 of FIG. 57E and the SV test mode decode 2 circuits920 of FIG. 57F.

[0546] An example of the test option logic 914 is illustrated as anelectrical schematic in FIG. 57C. The logic illustrated in FIG. 57C isbut one example of how the test mode logic 914 of FIG. 56 may beimplemented.

[0547] One example of an electrical schematic for implementing thesupervolt circuit 916 is illustrated in FIG. 57D. The purpose of thesupervolt circuit 916 is to prevent a powerup when the chip is in asupervoltage mode.

[0548] An electrical schematic illustrating one example of a test modedecode circuit 918 is illustrated in FIG. 57E. Test mode decode circuit918 is employed to decode certain column address bits to activate asupervolt test mode enable signal (SVTMEN*) when a signal (TMLATCH),indicating that the supervoltage mode is to be looked for, is latched.By latching a test or detect mode with latches 906, 907, if the addresssignal is correct or a match, then initiation of a test mode begins withthe SVTMEN* signal being activated. Latch 906 latches a supervoltageenable test mode at a RAS active (low) time. Latch 907 latches thesupervoltage enable test mode after RAS goes inactive (high) and theWLTON 1 signal is inactive. That allows other test mode(s) to be lookedat or entered provided signal NCSV (FIG. 57D) goes to a supervoltagelevel. Test mode decode circuit 918 provides the signal SVTMEN* to thesupervolt circuit 916 (FIG. 57D) and test mode enable latch 912 (FIG.57B). Supervolt circuit 916, in response to the signal SVTMEN*,activates the supervolt signal SV when the signal NCSV is in thesupervolt mode. The signal SV is provided to the test mode reset circuit910 of FIG. 57A and the test mode enable circuit latch 912. To preventinadvertent access, two cycles are needed to enter a test mode to testmode decode circuit 918 (FIG. 57E). In one embodiment, a first WCBRcycle is used to initiate a ready state; a second WCBR cycle is used toactually enter a test mode state. That makes it more difficult toinadvertently enable supervoltage and enter a test mode state. If thetest mode enable latch 912 is active, either the signal SVTMLATCHH orthe signal SVTMLATCHL (FIG. 57B) will be active for activating certainof the supervolt test mode decode 2 circuits 920 of FIG. 57F.

[0549] The SV test mode decode 2 circuits 920, of which there are eight,are illustrated in detail in FIG. 57F together with the respectiveoutput buses 921. The reader should realize that the electricalschematic illustrated in the bottom portion of FIG. 57F may be used toimplement the other SV test mode decode 2 circuits as well as the factthat other combinations of logic gates may be used to implement thatfunctionality. Also shown in FIG. 57F is the optprog driver circuit 922which produces the signal OPTPROG* which is input to the option logic658.

[0550] The SV test mode decode 2 circuits 920 receive column addressfuse identification signals (CAFID), column address test mode bitsignals, test mode latch signals (SVTMLATCH), and fuse identificationselect signals (FIDBSEL), in addition to the TMSLAVE signal, TMSLAVE*signal, and supervolt test mode reset signal (SVTMRESET). The number ofcolumn address test mode bit signals depend on array size, number oftest modes, number of fuse identifications, multiplexing, and the like.Each of the SV test mode decode 2 circuits 920 provides test modesignals TM, TM*, as well as fuse identification signals FIDDATA,FIDDATA*. While the signals FIDDATA indicate fuse ID, it should beunderstood that technology other than fuses, such as latches, flashcells, ROM cells, antifuses, RAM cells, mask programmed cells, or thelike, may be used.

[0551] With continuing reference to FIG. 57F, SV test mode decode 2circuit 920 receives column address bits via inputs A0 and A1. Such bitsmay be multiplexed. Bits received by a NOR gate 1262 are for identifyinga selected test mode. The column address fuse ID signal (CAFID) issupplied to a NAND gate 1263 along with the fuse ID select signal(FIDBSEL). The signal FIDBSEL is for selecting a fuse bank while thesignal CAFID is for selecting a bit of a selected bank.

[0552] A signal available at an output terminal of the NAND gate 1263 isinput directly to an inverting tri-state buffer 1264 and is input to thebuffer 1264 through an inverter 1265. When the output of the NAND gate1263 is inactive, output buffer 1264 is tri-stated. When the output ofthe NAND gate 1265 is active, data signals FIDDATA, FIDDATA* are activesuch that information is output. The TMSLAVE and TMSLAVE* signals arefor setting a latch 1266 formed by a pair of multiplexers. The signalTMLATCH is for setting a latch 1267 formed by another pair ofmultiplexers. As the column address bit information is processed, a testmode can be latched by the latch 1267 via signal TMLATCH. The latchedtest mode status of latch 1267 is provided to latch 1266 resulting inthe output of the signal SEL32MTM after RAS and WLTON go inactive. Adiscussion of a timing diagram for test mode entry is set forthhereinbelow in conjunction with FIG. 103.

[0553] An electrical schematic illustrating one implementation of theredundant test circuit 923 is illustrated in FIG. 57G. The circuit 923produces redundant row and redundant column signals as illustrated.

[0554] The Vccp clamp shift circuit 924 is illustrated in FIG. H. Thecircuit 924 is used to shift the voltage level of the input signal.Other types of clamp shift circuits may be implemented.

[0555]FIG. 57I illustrates an example of a DVC2 up/down circuit 925. Thecircuit 925 produces the signals DVC2 up* and DVC2 down which are inputto the DVC2 up circuit 1069 and the DVC2 down circuit 1070,respectively, both of which are illustrated in FIG. 72B.

[0556] In FIG. 57J an example of a DVC2OFF Circuit 926 is illustrated.The circuit 926 produces the signal DVC2OFF which is input to the enable1 circuit 512 illustrated in FIG. 42B.

[0557]FIG. 57K illustrates the Pass Vcc circuit 927. Other ways ofimplementing the functionality provided by the circuit 927 may beimplemented.

[0558]FIG. 57L illustrates an implementation for the TTLSV circuit 928.The primary function of the circuit 928 is to delay the signal TTLSVPAD.

[0559] Lastly, a disred circuit 929 is illustrated in FIG. 57M. Thecircuit 929 may be implemented by a Nor gate as shown in the figure.

[0560] The next element of FIG. 43 to be described is the option logic658 which is illustrated as a block diagram in FIGS. 58A and 58B. InFIG. 58A, a plurality of both fuse 2 circuits 930 through 940 areresponsive to a number of external signals. The both fuse 2 circuits 932through 940 are responsive to an SGND circuit 941 while the both fuse 2circuits 930, 931 are responsive to a second SGND circuit 942.

[0561] An ecol delay circuit 944 provides input to an anti-fuse cancelenable circuit 945.

[0562] In FIG. 58B, a first CGND circuit 946 is responsive to an OPTPROGsignal and a CGND Probe signal. Additional CGND circuits 947-951 areresponsive to an XA<10> signal; CGND circuit #947 is responsive to theOPTPROG signal, and CGND circuit 948-951 are responsive to an ANTIFUSEsignal.

[0563] Returning to FIG. 58A, an anti-fuse program enable circuit 956produces a signal input to a plurality of passgate circuits 952 through955. A PRG CAN decode circuit 957 is responsive to the passgate 952, aPRG CAN decode circuit 958 is responsive to the passgate circuit 953,and FAL circuits 959 and 960 are responsive to both the passgate 952 andthe passgate 954.

[0564] Bond option circuits 965, 966 produce input signals which areinput to a bond option logic circuit 967.

[0565] Two laser fuse option circuits 970 and 971 are also provided. Inaddition to the laser fuse option circuits 970, 971, a bank of laserfuse option 2 circuits 978 through 982 (See FIG. 58B) are provided. Thelaser fuse option 2 circuits 978 through 982 are responsive to a regpretest circuit 983.

[0566] Completing the description of FIG. 58A, the option logic 658 alsoincludes a 4K logic circuit 985, a fuse ID circuit 986, a DVC2E circuit987, a DVC2GEN circuit 988, and a 128 Meg circuit 989.

[0567] An electrical schematic of one type of circuit which may be usedas the both fuse 2 circuits 930 through 940 is illustrated in FIG. 59A.The external signals which are on a bus which interconnects all of theboth fuse 2 circuits 931 through 940 is illustrated in FIG. 59B as isthe 120 Meg circuit 989.

[0568]FIG. 59C illustrates an electrical schematic of one type of SGNDcircuit 941.

[0569] One embodiment of the ecol delay circuit 944 and the antifusecancel enable circuit 945 is illustrated in detail in FIG. 59D. Thecircuits 944 and 945 cooperate to produce the LATMAT signal.

[0570]FIG. 59E illustrates an electrical schematic of the CGND circuit951, which may be used to implement the other CGND circuits 947-951, aswell as the interconnection of the CGND circuits 946-951.

[0571]FIG. 59F illustrates one implementation for the passgates 952-955,anti-fuse program enable circuit 956, PRG decode circuits 957, 958, andFAL circuits 959, 960. The reader should understand that the detailsillustrated in FIG. 59F are but one method of implementing thefunctionality of that circuitry.

[0572] An electrical schematic for implementing the bond option circuits965, 966 is illustrated in FIG. 59G as is the bond option logic circuit967. The purpose of the bond option circuits 965, 966 and the bondoption logic 967 is to determine the bond option selected and to producelogic signals instructing the part if it is an ×4, ×8 or ×16 part.

[0573] The laser fuse option circuits 970, 971 are illustrated in FIG.59H. FIG. 59H illustrates one type of circuit implementation for theoption. Other types of fuse option circuits may be provided.

[0574]FIG. 59I illustrates one of the laser fuse opt 2 circuits 978 aswell as the interconnections between the reg pretest circuit 983 and thelaser fuse opt 2 circuits 978-982. The circuitry used to implement thelaser fuse opt 2 circuit 978 may be used to implement the circuits979-982.

[0575]FIG. 59J is an example of how the 4 k logic circuit 985 may beimplemented. The 4 k logic circuit produces signals which are ultimatelyused by the voltage supplies of the chip to determine the amount ofpower which must be produced. For example, recall that the 4 k signal isinput to the pump circuits 413-415 comprising the secondary group 423 tocontrol the operation of those pump circuits (see FIG. 39).

[0576] The construction of the fuse ID circuit 986 is illustrated inFIGS. 59K and 59L. The fuse ID circuit may be comprised of eightmultibit banks. The banks may be used to store unique information aboutthe part such as part number, position on the die, etc.

[0577] Finally, FIGS. 59M and 59N illustrate the details of oneimplementation of the DVC2E circuit 987 and the DVC2GEN circuit 988,respectively.

[0578] Completing the description of the block diagram illustrated inFIG. 43, the spare circuit 660 is shown in detail in FIG. 590 and themiscellaneous signal input circuit 662 is illustrated in detail in FIG.59P. The spare circuit 660 illustrates various additional componentswhich may be fabricated to provide spares for repair purposes. Themiscellaneous signal input circuit 662 illustrates a plurality of padsat which signals may be input or available.

[0579] IX. Global Sense Amp Drivers

[0580] The global sense amp driver 29 illustrated in FIG. 3C isillustrated in block diagram form in FIG. 60. As seen in FIG. 3C, asubstantial number of signals generated by the right logic 19 are input,vertically as shown in FIG. 3C, into global sense amp driver 29. It isthe function of global sense amp driver 29 to reorient those signals 900and in some cases decode or produce signals therefrom for input to thecircuits in the horizontal space existing between the rows of individual256K arrays 50 making up left 32 Meg array block 25 and right 32 Megarray block 27. The global sense amp drivers 35, 42, and 49 areidentical in construction and operation to the global sense amp driver29 such that only one will be described.

[0581] As shown in the block diagram of FIG. 60, the global sense ampdriver 29 is comprised of alternating row gap drivers 990, of whichthere are seventeen, and sense amp driver blocks 992, of which there aresixteen in this embodiment. The row gap drivers 990 determine which ofthe sixteen strips is enabled. An example of one type of sense ampdriver block 992 which may be used in connection with the presentinvention is illustrated in FIG. 61. An electrical schematic of one typeof row gap driver 990 which may be used in connection with the presentinvention is illustrated in FIG. 62. Those of ordinary skill in the artwill recognize that many types of row gap drivers 990 and sense ampdriver blocks 992 may be provided.

[0582] Sense amp driver block 992 includes an isolation driver 994 whichreceives an enable signal and a select signal to produce the ISO* signalused to drive the isolation transistors 83 shown in FIG. 6C. Thecondition of the isolation driver 994 is controlled by the state of theenable signal.

[0583] The isolation driver 994 is illustrated in detail in FIG. 63. Theisolation driver 994 includes a control circuit 995 which is responsiveto an internal signal 1004 generated by a detector circuit 998. Thecontrol circuit 995 is also responsive to the enable signal ENISO andthe select signal SEL32M. The control circuit 995 includes an enablecircuit 996, which ensures that all devices connected to the pumpedpotential are disabled when the isolation driver 994 is disabled. Thedetector circuit 998 monitors a first driver circuit 999, which circuitincludes a transistor 1003, and generates the internal signal 1004 todeactivate the first driver circuit 999 when an output node 1000 isdriven to the supply voltage. The detector circuit 998 includes apull-down transistor 1001 to prevent latch-up. A second driver circuit1002 is responsive to the internal signal 1004 produced by the detectorcircuit 998 to couple the output node 1000 to the pumped potential. Inthat manner, latch up within the isolation driver 994 is prevented whenthe isolation driver is disabled.

[0584] X. Right and Left Logic

[0585]FIGS. 64A, 64B, 65A, and 65B are high level block diagramsillustrating the right and left logic 19 and 21, respectively, of thepresent invention. The right logic 19 and left logic 21 are eachassociated with two 64 Meg array quadrants. As illustrated above in FIG.2, the right logic 19 is associated with array quadrants 14 and 15 andthe left logic 21 is associated with array quadrants 16 and 17. Theright and left logic 19 and 21 are very similar to each other in bothconstruction and operation. The right logic 19 is comprised of a leftside and a right side, illustrated in FIGS. 64A and 64B, respectively.The sides are not identical because, as described below, some functionsare performed for both sides by a single circuit.

[0586] As illustrated in FIG. 64A, the left side of the right logic 19includes a 128 Meg driver block A 1010 and a 128 Meg driver block B1012, each of which drive signals used by many circuits in the rightlogic 19. The architecture of the present invention allows for aclock-tree distribution of control signals, with some signals beingredriven several times. The 128 Meg driver block A 1010 receives anddrives predecoded row address signals RAnm<0:3>, ODD and EVEN signals,and control signals, such as ISO* and EQ*, for the sense amp elements.The 128 Meg driver block A 1010 is illustrated in detail in FIG. 66.

[0587]FIG. 67 is a block diagram of the 128 Meg driver block B 1012,which includes a row address driver 1014 for driving additionalpredecoded row address signals RA910<0:3> and RA1112<0:3>, and columnaddress delay circuits 1016 for delaying predecoded column addresssignals CAnm<0:3>. The column address signals are delayed to allow timeto determine if a redundant column should be fixed. Details of the rowaddress driver 1014 and column address delay circuits 1016 areillustrated in FIGS. 68A and 68B, respectively.

[0588] Referring back to FIG. 64A, the right logic 19 includes a numberof decoupling elements 1017. A decoupling element 1017, illustrated indetail in FIG. 69, may be embodied as two decoupling capacitors 44together with an associated transistor 1019. The decoupling elements1017 are distributed around the right logic 19 to stabilize voltagelevels and to prevent localized voltage fluctuations. Generally, theconcentration of decoupling elements 1017 in a given region of the rightlogic 19 is proportional to the power consumption in that region. If toofew decoupling elements 1017 are present, power levels will fluctuate ascomponents turn on and off, and power levels will vary from one locationto another.

[0589] The right logic 19 also includes four global column decoders1020-1023, one for each 32 Meg array block associated with the rightlogic 19. The 32 Meg array blocks are discussed in detail hereinabove inSection II. Closely associated with each global column decoder 1020-1023is a column address driver block 1026-1029, and an odd/even driver1032-1035, respectively. Associated with the column decoders 1020, 1021are a column address driver block 2 1038 and a column redundancy block1042; associated with the column decoders 1022, 1023 are a columnaddress driver block 2 1039 and a column redundancy block 1043.

[0590] The odd/even drivers 1032-1035 drive signals ODD and EVEN tocircuits in the global column decoders 1020-1023. One of the odd/evendrivers 1032 is illustrated in detail in FIG. 70. Signal SEL32M<n>enables the odd/even drivers 1020-1023 and is indicative of whether the32 Meg array block associated with the odd/even drivers 1020-1023 isenabled.

[0591] Each column address driver block 1026-1029 determines whether the32 Meg array block associated with it is enabled. If the 32 Meg arrayblock is enabled, an enable signal is provided to the column addressdriver block 2 1038, 1039 and column address signals are provided to theglobal column decoders 1020, 1021 or 1022, 1023, respectively. If the 32Meg array block is not enabled, the column address driver block1026-1029 discontinues the column address signals. The column addressdriver blocks 1026-1029 are discussed in more detail below inconjunction with FIG. 74.

[0592] Each side of the right logic 19 includes only one column addressdriver block 2. Column address driver block 2 1038 is responsive toenable signals from the column address driver blocks 1026, 1027, andcolumn address driver block 2 1039 is responsive to enable signals fromthe column address driver blocks 1028, 1029. Only one enable signal isrequired to enable each column address driver block 2 1038, 1039. Onceenabled, they provide column address data to the column redundancyblocks 1042, 1043, respectively. The column address driver block 2 1038and 1039 are discussed in more detail below in conjunction with FIG. 76.

[0593] Only two column redundancy blocks 1042, 1043 are present in theentire right logic 19, one in the left side and one in the right side.Each of the column redundancy blocks 1042, 1043 is associated with two32 Meg array blocks and two global column decoders 1020, 1021 and 1022,1023, respectively. The column redundancy blocks 1042, 1043 receivecolumn address signals from the column address driver block 2 1038,1039, respectively, and determine whether the columns being accessedhave been replaced with redundant columns. Information regardingredundant columns is provided to the appropriate global column decoder1020, 1021 in the case of column redundancy block 1042, and theappropriate global column decoder 1022, 1023 in the case of columnredundancy block 1043. The column redundancy blocks 1042, 1043 arediscussed in more detail below in conjunction with FIG. 78.

[0594] The global column decoders 1020-1023 receive informationregarding redundant columns, column address signals, and row addresssignals, and provide address signals to the 32 Meg array blocks. Theglobal column decoders 1020-1023 are discussed in more detail below inconjunction with FIG. 82.

[0595] The right logic 19 also includes four row redundancy blocks1046-1049, one for each 32 Meg array block. The row redundancy blocks1046-1049, in a manner analogous to the column redundancy blocks1042-1043, determine whether a row address has been logically replacedwith a redundant row and produce output signals indicative thereof. Theoutput signals from the row redundancy blocks 1046-1049 are driven byrow redundancy buffers 1052-1055, respectively, and are also provided,via topo decoders 1058-1061, respectively, to the datapath 1064. Thedatapath 1064 is discussed in more detail hereinabove in Section IV.

[0596] The right logic 19 includes certain of the Vccp pump circuits403, the Vbb pump 280, and four DVC2 generators 504, 505, 506, and 507,one for each 32 Meg array. The Vccp pump circuits are described inconjunction with FIG. 39, the Vbb pump 280 is described in conjunctionwith FIG. 37, and the DVC2 generators are described in conjunction withFIG. 41, hereinabove.

[0597] The right logic 19 also includes array V switches 1080-1083 andassociated array V drivers 1086-1089, respectively. FIG. 71A illustratesone of the array V drivers 1086-1089. The array V drivers 1086-1089 arecomprised primarily of two level translators 1094 and 1095 and twoinverters 1096 and 1097. The array V drivers 1086-1089 translate signalsto levels high enough to drive the array V switches 1080-1083,respectively. The array V drivers 1086-1089 each drive one of thesignals SEL32M*<2:5> to a corresponding array V switch 1080-1083,respectively. Each of the array V drivers 1086-1089 also produces one ofthe signals ENDVC2<2:5> and provides it to an associated array V switch1080-1083, respectively. Signals SEL32M*<2:5> are indicative of whethereach of the four 32 Meg array blocks associated with the right logic 19is enabled. Each one of the signals ENDVC2L<2:5> is indicative ofwhether an associated one of the DVC2 generators 504, 505, 506, and 507is enabled. Each of the array V switches 1080-1083, one of which isshown in detail in FIG. 71B, receives one of the signals SEL32M*<n>, andproduces one of the signals Vccp<n>. Similar functionality can be usedto switch the voltage Vcca.

[0598]FIG. 72A illustrates the details of the DVC2 switch 1066 shown inFIG. 64B. The DVC2 switch 1067 may be implemented in the same manner asthe switch 1066. The DVC2 switches 1066, 1067 receive signals AVC2<2:5>and DVC2<2:5>, respectively. Because both DVC2 switches 1066, 1067 areidentical in construction but receive different signals, FIG. 72A usessignal DVC2I<0:3> to represent signal AVC2<2:5> in the case of DVC2switch 1066. In the case of DVC2 switch 1067, signal DVC2<2:5> is used.The DVC2 switches 1066, 1067 are responsive to signals SEL32<n> andDVC2OFF, and can connect signals DVC2I<n> to DVC2PROBE. DVC2PROBE isconnected to a probe pad and can be measured with a probe, for example,during testing of the DRAM. DVC2PRIBE is connected to ground when not ina test mode.

[0599]FIG. 72B illustrates the details of the DVC2 up circuit 1069 andDVC2 down circuit 1070 illustrated in FIG. 64B. The circuits 1069 and1070 regulate the voltage level of the voltage DVC2 received by the DVC2switch 1066 in response to signals DVC2 up and DVC2 down, respectively.When the voltage DVC2 is too high, the signal DVC2 down turns on thetransistor in circuit 1070 which tends to pull the voltage DVC2 toground. Conversely, when the voltage DVC2 is too low, the signal DVC2 upturns on the transistor in circuit 1069 which tends to pull the voltageDVC2 up toward the voltage Vccx.

[0600] The right logic 19 includes a DVC2 NOR circuit 1092, illustratedin detail in FIG. 73. The DVC2 NOR circuit 1092 logically combinessignals DVC2OK*<n> generated by the four DVC2 generators 504, 505, 506,and 507. Logic gate 1073 produces a signal indicative of all of the DVC2generators being good while logic gate 1072 produces a signal if any ofthe DVC2 generators is good. Switches 1074 are set to conduct thedesired DVC2OK signal to an output terminal of circuit 1092.

[0601] Some of the components identified above will now be described inmore detail. Unless stated otherwise, the following description is madewith respect to the left side of the right logic 19, which isillustrated in FIG. 64A. In particular, the description is made withrespect to the components located in the bottom portion of FIG. 64A,associated with the 32 Meg array block 31 on the left side of quadrant15, as illustrated in FIG. 2. As with the electrical schematics andwiring diagrams previously shown, the following electrical schematicsand wiring diagrams are being provided for exemplary purposes and notfor limiting the claims to any particular preferred embodiment.

[0602]FIG. 74 is a block diagram of the column address driver block 1027illustrated in FIG. 64A. The column address driver block 1027 includesan enable circuit 1110, a delay circuit 1112, and five column addressdrivers 1114. The enable circuit 1110 determines whether the 32 Megarray block 31 is enabled and generates signals 32MEGEN and 32MEGEN*.Signal 32MEGEN is output to enable the column address driver block 2,1038 and signal 32MEGEN* is provided to the delay circuit 1112 andeventually enables the column address drivers 1114. The delay is neededto determine if a redundant column should be fired. Once the columnaddress drivers 1114 are enabled, they drive the column address signalsCAnm*<0:3> for use by the global column decoder 1021.

[0603]FIG. 75A illustrates the enable circuit 1110 for producing signals32MEGEN* and 32MEGEN. FIG. 75B illustrates the delay circuit 1112 as aseries of inverters which delay the propagation of the signal 32MEGEN*.The delay is increased by capacitors connected to an output terminal andan input terminal of two series connected inverters. The delay circuit1112 produces a signal EN* for enabling the column address drivers 1114.The purpose of the delay circuit 1112 is to prevent the column addressdrivers 1114 from being enabled before the column redundancy canevaluate a new column address.

[0604]FIG. 75C illustrates one of the column address drivers 1114. Eachcolumn address driver 1114 receives column address signals CAnm*<0:3>,is enabled by signal EN*, and produces output signals LCAnm*<0:3> inputto the global column decoder 1021.

[0605]FIG. 76 illustrates a block diagram of the column address driverblock 2 1038 which services the entire left side of the right logic 19.The column address driver block 2 1038 drives column address signalsCAnm*<0:3> to the column redundancy block 1042. The column addressdriver block 2 1038 includes a NOR gate 1120 and five column addressdrivers 1122. The NOR gate 1120 receives signals 32MEGENa and 32MEGENbfrom column address driver blocks 1026 and 1027, respectively, andproduces an enable signal EN* for the column address drivers 1122. Ifeither of signals 32MEGENa and 32MEGENb is a logic high, the NOR gate1120 will enable the column address drivers 1122.

[0606]FIG. 77 illustrates one of the column address drivers 1122. Eachcolumn address driver 1122 receives column address signals CAnm*<0:3>,is enabled by signal EN* from the NOR gate 1120, and produces outputsignals LCAnm*<0:3>input to the column redundancy block 1042.

[0607]FIG. 78 is a block diagram of the column redundancy block 1042.The column redundancy block 1042 services both the top and bottomportions of the left side of the right logic 19 and is comprised of twosets of eight identical column banks 1130. The first set 1132 of eightcolumn banks 1130 serves global column decoder 1020 and the second set1134 of eight column banks 1130 serves global column decoder 1021. Thepurpose of the column redundancy block 1042 is to determine whether acolumn address matches a redundant column address. Such matching willoccur whenever a column has been logically replaced with a redundantcolumn.

[0608]FIG. 79 is a block diagram of one of the column banks 1130 shownin FIG. 78. The column bank 1130 includes four column fuse blocks1136-1139. All of the column fuse blocks 1136-1139 may be programmed byopening fuses with a precision laser, and one of the column fuse blocks1136 may also be programmed electrically. The column fuse blocks1136-1139 receive column address signals and produce column matchsignals CMAT*<0:3> which are indicative of a match between a columnaddress and a redundant column. The CMAT* <0:3> signals cancel columnselect signals CSEL produced by the global column decoder 1021, andenable redundant column select signals RCSEL.

[0609]FIG. 80A is a block diagram of the column fuse block 1136 shown inFIG. 79. The column fuse block 1136 contains four column fuse circuits1144, each of which receives column address signals CAnm*<0:3> andproduces a column address match signal CAM* indicative of whether thecolumn address signals match a portion of a redundant column address. Anenable circuit 1146 produces an enable signal EN indicative of whetherthe column fuse block 1136 is enabled. The output signals CAM* and theenable signal EN* are combined in output circuit 1148 to produce acolumn match signal CMAT*, indicative of whether there is a matchbetween a column address and a redundant column. Details of the outputcircuit 1148 are illustrated in FIG. 80B.

[0610]FIG. 80C illustrates the details of one of the columns fusecircuits 1144 shown in FIG. 80A. The column fuse circuit 1144 containstwo fuses which may be opened to represent two bits of a redundantcolumn address. Associated with each fuse is a latch, comprising twoinverters in a feedback loop. Once enabled by column fuse power signalsCFP and CFP* generated by the enable circuit 1146, the latches read thefuses and latch the data. The latches are generally enabled on powerupand during RAS cycles. The data in the latches is predecoded into trueand complement signals and provided, along with the column addresssignals CAnm*<0:3>, to comparator logic for producing signal CAM*.

[0611]FIG. 80D illustrates details of the enable circuit 1046 shown inFIG. 80A. The enable circuit 1046 contains two fuses, one for enablingthe fuse block 1136, and one for subsequently disabling the fuse block1136 in the event the fuse block 1136 itself becomes defective. Theenable circuit 1046 feeds the column fuse power signals CFP and CFP* forthe column fuse circuits 1144 and a feedback signal EFDIS<n> indicativeof whether the fuse block 1136 is disabled.

[0612] Referring back to FIG. 79, column electric fuse circuits 1150 anda column electric fuse block enable circuit 1152 provide signals to theelectrically programmable column fuse block 1136. A fuse block selectcircuit 1154 receives the column address signals CAnm*<0:3>and producesa fuse block select signal FBSEL* indicative of whether the fuse blocks1136-1139 are enabled. A CMATCH circuit 1156 receives the signalsCMAT*<0:3> from the column fuse blocks 1136-1139 and produces signalsCELEM and CMATCH* indicative of whether there is a match between acolumn address and a redundant column. Details of the column electricfuse circuits 1150, column electric fuse block enable circuit 1152, fuseblock select circuit 1154, and CMATCH circuit 1156 are illustrated inFIGS. 81A, 81B, 81C, and 81D, respectively.

[0613]FIG. 82 is a block diagram of the global column decoder 1021 shownin FIG. 64A. The global column decoder 1021 includes four groups ofcolumn drivers, with each group having two column decode CMAT drivers1160, 1161 and one column decode CA01 driver 1164. Each group of columnCMAT drivers 1160, 1161 and column decode CA01 driver 1164 providessignals to a pair of global column decode sections 1170, 1171. Theglobal column decoder 1021 also includes nine row driver blocks 1166.Each row driver block 1166 drives row address data to produce rowaddress signals nLRA12<0:3>, nLRA34<0:3>, and nLRA56<0:3> for use by the32 Meg array block 31. FIG. 83A illustrates the details of one of therow driver blocks 1166.

[0614] Each pair of column decode CMAT drivers 1160, 1161 are enabled byone of signals CA1011*<0:3> and collectively drive eight of theCMAT*<0:31> signals. Each of the column decode CA01 drivers 1164 isenabled by two of the signals CELEM<0:7> and each drives the signalsCA01*<0:3>. FIGS. 83B and 83C illustrate the details of one of thecolumn decode CMAT drivers 1160 and one of the column decode CA01 driver1164, respectively.

[0615] Each of the global column decode sections 1170, 1171 are enabledby signals LCA01<0:3> and further predecode a group of column addresssignals to produce 132 column select signals CSEL for use by the 32 Megblock array 31. A total of 1056 column select signals CSEL<0:1055> aregenerated by all of the global column decode sections.

[0616]FIG. 83D is a block diagram of one of the global column decodesections 1170. The global column decode section 1170 is comprised of aplurality of column select drivers 1174 and R column select drivers1176.

[0617]FIGS. 84A and 84B illustrate one of the column select drivers 1174and R column select drivers 1176, respectively, found in the globalcolumn decode sections 1170, 1171.

[0618]FIG. 85 is a block diagram of the row redundancy block 1047illustrated in FIG. 64A. The row redundancy block 1047 includes eightidentical row banks 1180 for comparing a portion of a row addressRAnm<0:3> to a portion of a redundant row address and for producing rowmatch signals RMAT indicative of a match. Redundant logic 1182 logicallycombines the RMAT signals and produces output signals indicative ofwhether the row address RAnm<0:3> has been replaced with a redundantrow. The redundant logic 1182 is shown in detail in FIG. 86.

[0619] In FIG. 86, the redundant logic 1182 receives the row matchsignals RMAT <n>. A node 1183 is charged to a high level. If any of theRMAT signals goes high, the node 1183 is discharged which is captured ina latch. If the signal ROWRED <n> stays low, then there is no redundancymatch. Under those circumstances, the normal row is used. If the signalROWRED <n> goes high, then one of the redundancy rows is to be used andthe particular signal which goes high identifies the phase to be fired.

[0620] The redundant logic 1182 also receives the fuse address latchsignal FAL which is combined with other signals to produce the RMATCH*signal, which is used for programming. The redundant logic 1182 alsoreceives all of the ROWRED signals and combines them to produce a signalRELEM* which indicates that there is a match somewhere in the redundantlogic. That signal is used to create the redundant (RED) signal.

[0621]FIG. 87 is a block diagram of one of the row banks 1180illustrated in FIG. 85. The row bank 1180 includes one row electricalblock 1186 which may be programmed either electrically or with aprecision laser, and three row fuse blocks 1187-1189 which may beprogrammed only with a precision laser. The row electrical block 1186and row fuse blocks 1187-1189 receive row address signals RAnm<0:3> andproduce output signals RMAT<0:3> indicative of whether a row addressmatches a redundant row. Rsect logic 1192 receives the signals RMAT<0:3>and produces a signal RSECT<n> indicating which array section has aredundant match. The details of the rsect logic 1192 are illustrated inFIG. 88.

[0622]FIG. 89 is a block diagram of the row electric block 1186illustrated in FIG. 87. The row electric block 1186 includes sixelectric banks 1200-1205 which receive row address signals and producesignals RED* indicative of whether there is a match between a rowaddress and a redundant row. The addresses of redundant rows arerepresented electrically by signals EFnm<0:3>. A redundancy enablecircuit 1208 is programmable with fuses to enable and disable the rowelectric block 1186, and to produce a signal PR to enable the electricbanks 1200-1205 and an electric bank 2 1210. A select circuit 1212 andthe electric bank 2 1210 receive row address signals and produce signalsG252 and RED*, respectively, indicative of whether the row electricblock 1186 is enabled. Like the electric banks 1200-1205, the electricbank 2 1210 compares row address data, represented by signals EVEN andODD, to electrical signals EFeo<0:1>. An output circuit 1214 receivessignals RED* from the electric banks 1200-1205 and signals G252 and RED*from the select circuit 1212 and the electric bank 2 1210, and producesrow match signal RMAT indicative of whether there is a match between arow address and a redundant row. Details of one of the electric banks1200, the redundancy enable circuit 1208, the select circuit 1212, theelectric bank 2 1210, and the output circuit 1214, are illustrated inFIGS. 90A, 90B, 90C, 90D, and 90E, respectively.

[0623]FIG. 91 is a block diagram of one of the row fuse blocks 1187illustrated in FIG. 87. The row fuse block 1187 includes fuse banks1220-1225, a fuse bank 2 1228, a redundancy enable circuit 1230, aselect circuit 1232, and an output circuit 1234. The components of therow fuse block 1187 are identical to the row electric fuse block 1186,except that redundant rows are represented by fuses in the fuse banks1220-1225 and fuse bank 2 1228 of the row fuse block 1187, rather thanwith electrical signals EFnm<0:3> and EFeo<0:1> in the row electricbanks 1200-1205 and row electric bank 2 1210 of the row electric block1186. Details of one of the fuse banks 1220, the redundancy enablecircuit 1230, the select circuit 1232, fuse bank 2 1228, and the outputcircuit 1234 are illustrated in FIGS. 92A-92E, respectively.

[0624] Referring back to FIG. 87, row electric pairs 1240-1245 and a rowelectric fuse 1248 provide signals EFnm<0:3> representing a redundantrow address to the row electrical block 1186. The row electric pairs1240-1245 and row electric fuse 1248 are enabled by fuse block selectsignal FBSEL* produced by input logic 1250, shown in more detail in FIG.93A. The row electrical block 1186 is enabled by signal EFEN, producedby row electric fuse block enable circuit 1252 illustrated in detail inFIG. 93B.

[0625]FIG. 93C illustrates the row electric fuse 1248 shown in FIG. 87.The row electric fuse 1248 includes an antifuse that can be shortedelectrically by applying a high voltage at signal CGND. The data storedin the antifuse is output as predecoded signals EFB*<0> and EFB<1>.

[0626]FIG. 93D illustrates one of the row electric pairs 1240 shown inFIG. 87. The row electric pairs 1240-1245 each store two bits of data, amost significant bit and a least significant bit, and include twoindependent and identical circuits, one for the most significant bit andone for the least significant bit. Each of the circuits store its bit ofdata with an antifuse that can be shorted by applying a high voltage atsignals CGND. The row electric pairs 1240-1245 also include a predecodecircuit for producing predecoded signals EFnm<0:3>.

[0627] Referring briefly back to FIG. 64A, the output of the rowredundancy block 1047 is driven by the row redundancy buffer 1053,illustrated in detail in FIG. 94. The output of the row redundancybuffer 1053 is also input to the topo decoder 1059, illustrated in FIG.95. The topo decoder 1059 produces signals TOPINVODD, TOPINVODD*,TOPINVEVEN, and TOPINVEVEN* which are input to the datapath 1064.

[0628] The left logic 21, illustrated in FIGS. 65A and 65B, is nearlyidentical to the right logic 19. Generally, components in the left logic21 use the same reference numbers, followed by a prime symbol “′”, asfunctionally-identical components in the right logic 19. Exceptions tothe numbering scheme are made for the Vccp pump circuits 402 and theDVC2 generators 500, 501, 502, and 503, which were introduced and aredescribed in more detail in Section VII.

[0629] The left logic 21 differs from the right logic 19 in that theleft logic 21 does not include a Vbb pump 280. Furthermore, the leftlogic 21 does include a data fuse id 1260, which is not present in theright logic 19. The data fuse id 1260 drives fuse id data through thedatapath 1064′ to one or more data pads. FIG. 96 illustrates the detailsof the data fuse id 1260. The data used in the data fuse id circuit 1260comes from the center logic.

[0630] XI. MISCELLANEOUS FIGURES

[0631]FIG. 97 illustrates the data topology of one of the 256K arrays 50shown in FIG. 4 which is constructed in accordance with the teachings ofthe present invention. The array 50 is constructed from a plurality ofindividual memory cells 1312, all of which are constructed in a similarmanner.

[0632]FIG. 98 illustrates the details of one of the memory cells 1312.Each memory cell 1312 includes first and second transistor/capacitorpairs 1314, 1315. Each of the transistor/capacitor pairs 1314, 1315include a storage node 1318, 1319, respectively. A contact 1320, sharedby the two transistor/capacitor pairs 1314, 1315, connects thetransistor/capacitor pairs 1314, 1315 to the wordlines WL<n>.

[0633] Referring back to FIG. 97, the memory array 50 has wordlinesWL<n> running horizontally and digitlines DIGa<n>, DIGa*<n>, DIGb<n>,and DIGb*<n> running vertically. The wordlines WL<n> overlay activeareas of the transistor/capacitor pairs 1314, 1315 and determine whethertransistors in the transistor/capacitor pairs 1314, 1315 are in aconductive or a non-conductive state. The wordline signals originatefrom row decoders located to the left and right of the memory array 10.The memory array 10 has 512 live wordlines WL<0:511>, two redundantwordlines RWL<0:1> located on the bottom of the memory array 50, and tworedundant wordlines RWL<2:3> located on the top of the memory array 50.The redundant wordlines may be logically substituted in place ofdefective wordlines. The digitlines are organized in pairs, with eachpair representing a true and a complement value for the same bit of datain the array 50. The digitlines carry data into or away from the digitalcontact 1320, and connect the digital contact 1320 to sense amps locatedon the top and bottom of the memory array 50. There are 512 digitlinepairs in the memory array, with an additional 32 redundant digitlinepairs.

[0634] The wordlines are preferably constructed of polysilicon while thedigitlines are preferably constructed of either polysilicon or metal.Most preferably, the wordlines are constructed of polysilicon that issilicided to reduce resistance and heat to thereby permit longerwordline segments without reducing speed. The storage nodes 1318 may beconstructed with an oxide-nitride-oxide dielectric between twopolysilicon layers.

[0635]FIG. 99 is a state diagram 1330 illustrating the operation of apowerup sequence circuit 1348 (shown in FIG. 100) which may be used tocontrol the powering up of the various voltage supplies and associatedcomponents of the chip 10. The state diagram 1330 includes a reset state1332, a Vbb pump powerup state 1334, a DVC2 generator powerup state1336, a Vccp pump powerup state 1338, a RAS powerup state 1340, and afinish powerup sequence state 1342. The Vbb pumps, the DVC2 generators,and the Vccp pumps are discussed hereinabove in Section VII.

[0636] When power is first applied to the chip 10, the powerup sequencecircuit 1348 begins in the reset state 1332. The purpose of the resetstate 1332 is to wait for the externally supplied voltage Vccx to reacha third predetermined value preferably below the first predeterminedvalue shown in FIG. 36B, before allowing the powerup sequence to begin.Once Vccx exceeds that third predetermined value, the sequence circuit1348 proceeds to the Vbb powerup state 1334. If Vccx ever falls belowthe third predetermined value, the sequence circuit 1348 will return tothe reset state 1332.

[0637] The purpose of the Vbb powerup state 1334 is to wait for the backbias voltage Vbb, provided by Vbb pumps 280, to reach a predeterminedvalue, preferably −1 volt or less, before proceeding with powering upadditional voltage supplies. The Vbb pumps 280 are automaticallyactivated when Vccx begins to rise, and they are usually still runningwhen the sequence circuit 1348 reaches the Vbb powerup state 1334. Whenthe voltage Vbb has reached its predetermined state, the Vbb pumps 280turn off and the sequence circuit 1348 leaves the Vbb powerup state 1334and proceeds to the DVC2 powerup state 1336.

[0638] The purpose of the DVC2 powerup state 1336 is to wait for thevoltage DVC2 to reach a predetermined state before proceeding withpowering up additional voltage supplies. That may mean waiting for allthe DVC2 generators to reach a steady state or just one depending uponhow the switches 74 are set in the DVC2 NOR circuit 1092 shown in FIG.73. When the voltage DVC2 has reached a predetermined state, andassuming that the voltages Vccx and Vbb are each in their desiredrespective predetermined states, the sequence circuit 1348 proceeds fromthe DVC2 powerup state 1336 to the Vccp powerup state 1338.

[0639] The purpose of the Vccp powerup state 1338 is to wait for thevoltage Vccp to reach a predetermined state, preferably aboveapproximately Vcc plus 1.5 volts. Before voltage Vccp can reach itspredetermined state, however, voltage Vcc must be in its predeterminedstate. Vcc usually does not delay the Vccp powerup state because, asmentioned above, Vcc is powered up during the reset state 1332. Once thevoltage Vccp has reached its predetermined state, and assuming that thevoltages Vccx, Vbb, and DVC2 are each in their desired respectivepredetermined states, the sequence circuit 1348 proceeds from the Vccppowerup state 1338 to the RAS powerup state 1340.

[0640] The purpose of the RAS powerup state 1340 is to provide power tothe RAS buffers 745 (shown in FIG. 46). The sequence circuit 1348 thenproceeds to a finish powerup sequence state 1342 where it remains untilVccx falls below the third predetermined value. At that time, thesequence circuit 1348 returns to the reset state 1332 and waits for Vccxto return to the third predetermined value.

[0641]FIG. 100 is a block diagram of one example of a powerup sequencecircuit 1348 constructed to implement the functionality of the statediagram 1330 illustrated in FIG. 99. A voltage detector 1350 receivesthe externally supplied voltage Vccx and generates an output signalUNDERVOLT* indicative of whether Vccx is above the third predeterminedvalue, preferably approximately two volts. FIG. 101A is an electricalschematic illustrating one example of a voltage detector 1350 which maybe used. The voltage detector 1350 includes a pair of parallel-connectedresistors, one of which is optioned out, in series with series-connectedpMOS transistors to form a first voltage limiting circuit 1352responsive to Vccx. The first voltage limiting circuit 1352 produces afirst threshold signal VTH1 seen in FIG. 101B at a junction between theresistors and the pMOS transistors. The first threshold signal VTH1 isused to gate a transistor of a first signal generating circuit 1354which produces a signal VSW when Vccx is above a fourth predeterminedvalue, preferably approximately 2.0 volts.

[0642] The voltage detector 1350 also includes a second voltage limitingcircuit 1356 and a second signal generating circuit 1358 which areconstructed and function in an analogous manner to the first voltagelimiting circuit 1352 and the first signal generating circuit 1354,respectively. The second voltage limiting circuit 1356 is constructed ofseries-connected nMOS transistors and a resistors, one of which isoptioned out. The circuit 1356 is responsive to Vccx and produces asecond threshold signal VTH2 seen in FIG. 101C. The second signalgenerating circuit 1358 is constructed of an nMOS transistor and a pairof parallel-connected resistors, is responsive to Vccx and VTH2, andproduces a second signal VSW2 indicative of whether Vccx is above thefourth predetermined value.

[0643] The signals VSW and VSW2 from the first and second signalgenerating circuits 1354, 1358, respectively, are logically combined ina logic circuit 1360 to produce the UNDERVOLT* signal indicative ofwhether both first and second signal generating circuits 1354, 1358indicate that Vccx is above the fourth predetermined value.

[0644] The voltage detector 1350 contains two pair of substantiallyidentical circuits to compensate for fabrication variances that maycause either NMOS devices or pMOS devices to operate in a differentmanner than anticipated. Such variances, if they occur, will likelycause one of the voltage limiting circuits 1352, 1356 or one of thesignal generating circuits 1354, 1358 to trigger sooner than expected,thereby prematurely indicating that Vccx is above the fourthpredetermined value. If that happens, the sequence circuit 1348 maybegin to operate before Vccx can reliably support operation of thecircuits, potentially resulting in errors. However, because the logiccircuit 1360 requires that both signal generating circuits 1354, 1358indicate Vccx is above the fourth predetermined value before UNDERVOLT*is produced in a high logic state, an error by any one of the circuits1352, 1354, 1356, 1358 will not adversely affect the performance of thevoltage detector 1350. It is, of course, possible that a fabricationvariance will cause one of the circuits 1352, 1354, 1356, 1358 totrigger too late, delaying one of the signals VSW or VSW2. That type ofvariance, however, is more easily corrected and, in any event, will notresult in the sequence circuit 1348 operating without sufficientvoltage. Other types of logic circuits 1360 may be used to effectdifferent results, e.g., production of the UNDERVOLT* signal when onlyone of the signals VSW and VSW2 is available.

[0645]FIG. 101D is an electrical schematic illustrating one example ofthe reset circuit 1362 which may be used. The reset logic 1362 receivesthe UNDERVOLT* signal and generates a signal CLEAR* indicative ofwhether UNDERVOLT* is stable. In the preferred embodiment, the resetcircuit 1362 determines that Vccx is stable if it is above two volts forat least a predetermined period of time, approximately 100 nanoseconds.The reset circuit 1362 includes a number of series-connected delaycircuits 1363 responsive to the signal UNDERVOLT*. The number of delaycircuits 1363, and the propagation delay associated with each one,largely determines the predetermined period of time that Vccx must beabove two volts before the reset circuit 1362 determines that Vccx isstable. The reset circuit 1362 also includes a reset logic gate,comprised of an inverter responsive to the signal UNDERVOLT* forproducing a reset signal RST to reset the delay circuits 1363. When theUNDERVOLT* signal goes to a low logic state, indicating that Vccx isless than the first predetermined value, the reset logic gate generatesa high logic state signal that discharges a capacitor in the delaycircuits 1363 as shown in FIG. 110E. By discharging the capacitor, thedelay is always the same. If a power “glitch” is relied upon todischarge the capacitor, the glitch might not be long enough tocompletely discharge the capacitor. Under such cases, the delay timewould become unpredictable.

[0646] The reset logic 1362 also includes a logic circuit comprising aNAND gate and an inverter that are responsive to both the UNDERVOLT*signal and to an output signal from the last delay circuit 1363. If boththe UNDERVOLT* signal and the output signal from the last delay circuit1363 are in a high logic state, then the logic circuit will generate aCLEAR* signal in a high logic state, indicating that Vccx is stable. If,however, the UNDERVOLT* signal goes to a low logic state at any time,the delay circuits 1363 will be reset and the logic circuit willgenerate the CLEAR* signal in a low logic state, indicating that Vccx isnot stable. The CLEAR* signal will remain in a low logic state until theUNDERVOLT* signal remains in a high logic state long enough for a signalto propagate through the delay circuits 1363 and through the logiccircuit. The reset logic 1362 is used in the preferred embodiment toprevent the sequence circuit 1348 from proceeding beyond the resetsequence state 1332 (shown in FIG. 99) before Vccx is both above thedesired predetermined value and stable. The reset logic 1362, however,is not required for the sequence circuit to implement the functionalityof the state diagram 1330 illustrated in FIG. 99.

[0647] A state machine circuit 1364 shown in FIG. 100 receives theCLEAR* signal from the reset logic 1362, and also receives other signalsindicative of the state of Vbb, DVC2, and Vccp. The state machinecircuit 1364 performs the functions illustrated in the state diagramshown in FIG. 99, as will be described in more detail below.

[0648] An alternative to the powerup sequence circuit 1348 is RC timingcircuits 1368, 1369. RC timing circuits 1368, 1369 generate powerupsignals based only on the passage of time since the application of theexternally supplied voltage Vccx, and they do not receive feedbacksignals. The RC timing circuits 1368, 1369 are provided as analternative to the sequence circuit 1348, but they are not required forthe sequence circuit 1348 to operate. FIG. 101F and FIG. 101G areelectrical schematics illustrating one embodiment of the RC timingcircuits 1368, 1369, respectively.

[0649] Output logic 1372 receives output signals from both the statemachine circuit 1364 and the RC timing circuits 1368, 1369. The outputlogic uses only one set of output signals, either from the state machinecircuit 1364 or from the RC timing circuits 1368, 1369. A STATEMACH*signal received by the output logic 1372 determines which set of outputsignals are used by the output logic 1372. FIG. 101H illustrates anelectrical schematic of one embodiment of the output logic 1372comprising a number of multiplexers controlled by the STATEMACH* signal.

[0650] Bond option 1374 allows for a selection between the use of thestate machine circuit 1364 or the use of the RC timing circuits 1368,1369. That selection is made, for example, by opening or not opening afuse within the bond option 1374 so as to generate the STATEMACH* signalfor use by the output logic 1372. FIG. 101I illustrates an electricalschematic of one embodiment of the bond option 1374.

[0651]FIG. 101J is an electrical schematic of one embodiment of thestate machine circuit 1364 shown in FIG. 100. A NOR gate 1379 receivesthe VBBON and VBBOK* signals and generates a VBBOK2 signal, which isprovided along with a CLEAR* signal to a spare circuit 1388. The sparecircuit 1388 is provided to allow for modifications of the DRAM in theevent an additional powerup state is desired at a later time. If theCLEAR* signal is in a high logic state, the VBBOK2 signal is passedthrough the spare circuit 1388 and provided to a DVC2 enable circuit1380. If the CLEAR* signal is in a low logic state, the spare circuit1388 generates a low logic signal for the DVC2 enable circuit 1380,indicating that Vccx is not stable. The DVC2 enable circuit 1380 alsoreceives the CLEAR* signal, and generates a DVC2EN* signal to enable theDVC2 generators 500 when the above-described conditions are met. SignalsDVC2OKR and DVC2OKL are indicative of whether DVC2 is determined to bewithin a predetermined range in the right and left logic 19, 21,respectively. A NAND gate 1377, whose output is coupled to an inverter1378, logically combines the DVC2OKR and DVC2OKL signals to produce theDVC2OK signal indicative of whether DVC2 is determined to be within apredetermined range in both the right and left logic 19, 21.

[0652] A Vccp enable circuit 1382 receives the CLEAR*, VBBOK2, andDVC2OK signals and generates the VCCPEN* signal to enable the Vccp pumps400 when the above-described conditions are met. An inverter 1383converts the VCCPON signal into its complement, VCCPON*. A power RAScircuit 1384 receives the CLEAR*, VBBOK2, DVC2OK, and VCCPON* signalsand generates the PWRRAS* signal to enable the RAS buffers 745 when theabove-described conditions are met. A RAS feedback circuit 1366 receivesa PWRRAS* signal and generates a RASUP signal indicative of whether theRAS buffers have been enabled.

[0653] A powered up circuit 1386 receives the CLEAR*, VBBOK2, DVC2OK,VCCPON*, and RASUP signals and generates the PWRDUP and PWRDUP* signalsto indicate that the chip 10 has reached a powered up state when theabove-described conditions are met. Each of the circuits 1380, 1382,1384, 1386, 1388 are comprised of a NAND gate receiving various signalsand a latch that is reset by the CLEAR* signal when Vccx is determinedto be unstable.

[0654] FIGS. 102A-102K are simulations of timing diagrams illustratingthe signals associated with the powerup sequence circuit 1348. FIG. 102Aillustrates Vccx as it ramps steadily upward as more external power isapplied.

[0655]FIG. 102B illustrates the UNDERVOLT* signal, which changes statefrom a low to a high logic state to indicate when the voltage Vccx hasreached or exceeded the first predetermined value.

[0656]FIG. 102C illustrates the CLEAR* signal, which is responsive tothe UNDERVOLT* signal and changes state from a low to a high logic stateafter the UNDERVOLT* signal has been in a high logic state for apredetermined period of time, preferably approximately 100 nanoseconds.The CLEAR* signal indicates that the externally supplied voltage Vccx isbelieved to be stable.

[0657]FIG. 102D illustrates the VBBOK2 signal. The VBBOK2 signal fallsfrom a high to a low logic state at a point in time indicated byreference number 1390 when the voltage Vbb reaches a predetermined stateand the Vbb pumps 280 turn off.

[0658]FIG. 102E illustrates the DVC2EN* signal, which is output from thesequence circuit 1348 to enable the DVC2 generators 500. As can be seenby comparing FIGS. 102D and 102E, the DVC2 generators 500 are notenabled until the signal VBBOK2 goes to a low logic state.

[0659]FIG. 102F illustrates the DVC2OKR signal, which is indicative ofwhether the voltage DVC2 is stable in the right logic. An analogoussignal indicative of the whether the voltage DVC2 is stable in the leftlogic, DVC2OKL, is provided to the sequence circuit 1348 illustrated inFIG. 100 but is not shown in the timing diagram because, under normalcircumstances, both DVCOKR and DVC2OKL react very similarly. The signalDVC2OKR does not indicate a stable state for the voltage DVC2 until atime indicated by reference number 1391.

[0660]FIG. 102G illustrates the VCCPEN* signal, which is output from thesequence circuit 1348 to enable the Vccp pumps 400. The signal VCCPEN*will not enable the Vccp pumps 400 until point 1392, when the CLEAR*signal is high, the VBBOK2 signal is low, and the DVC2OKR signal ishigh.

[0661]FIG. 102H illustrates the VCCPON signal, which is indicative ofwhether the Vccp pumps 400 are on after the pumps have been enabled.Prior to that time, its state is irrelevant.

[0662]FIG. 102I illustrates the PWRRAS* signal, which is output from thesequence circuit 1348 to provide power to the RAS buffers 745. ThePWRRAS* signal does not provide power to the RAS buffers 745 until apoint in time indicated by reference number 1393, when the CLEAR* signalis high, the VBBOK2 signal is low, the DVC2OKR signal is high, and theVCCPON signal is low.

[0663]FIG. 102J illustrates the RASUP signal, which is indicative ofwhether the RAS buffers 745 are receiving power.

[0664]FIG. 102K illustrates the PWRDUP* signal, which is output from thesequence circuit 1348 to indicate that the chip 10 has completed itspowerup sequence. The PWRDUP* signal does not indicate completion ofpowerup until a point in time indicated by reference number 1394, whenthe CLEAR* signal is high, the VBBOK2 signal is low, the DVC2OKR signalis high, the VCCPON signal is low, and the RASUP signal is high.

[0665] If, at any time during the powerup sequence, the external voltageVccx falls below the first predetermined value, the signal CLEAR* willgo low and reset the sequence circuit 1348, including the output signalsDVC2EN*, VCCPEN*, PWRRAS, and PWRDUP*.

[0666] Referring to FIG. 103, a test mode entry timing diagram isillustrated. Supervoltage WCBR test modes require a vectored WCBR toload the supervoltage enable test key. That is followed by a secondSVWCBR, to load the desired test key, but with the supervoltage appliedto the N/C (no connect) pin. Testkeys may be entered on CA0-7, and thetest mode will remain valid until the supervoltage is removed or theclear test mode key is asserted. Once the supervoltage enable test modehas been loaded into the DRAM, subsequent SVWCBRs will load inadditional test modes. For example, if mode 2 (discussed below) is to becombined with mode 4 (discussed below), then 1 WCBR and 2 SVWCBRs areperformed. The first WCBR will enable the supervoltage circuit and thenext two SVWCBRs load in key 2 and key 4 (see FIG. 103). To exit allselected test modes, including the supervoltage enable test mode, entereither the clear test mode key during a SVWCBR or drop the supervoltageon the N/C pin. All of the tests which can be performed on the DRAM areentered using this supervoltage test mode.

[0667] As shown in FIG. 103, two CAS before RAS cycles 1270, 1271 areused. Cycles 1270, 1271 correspond to edges 1272, 1273, 1274 and edges1275, 1276, 1277, of the write enable (WE*) signal, CAS* signal, andRAS* signal, respectively. During cycles 1270, 1271 the address signalmay provide address information for putting the chip 10 in a ready stateand a test mode state, respectively. At time 1280, which is after time1281 when RAS* goes inactive, if the WLTON 1 signal goes inactive low,then a test mode operation may be entered provided the access voltagesignal is at a supervoltage level.

[0668] According to the present preferred embodiment of the invention,the test modes which can be entered are as follows:

[0669] 0. CLEAR—This testkey will disable all test modes previouslyentered by WCBR cycles, including the supervoltage enable.

[0670] 1. DCSACOMP—This test mode provides 2× address compressionwithout writing adjacent bits or crossing redundancy regions bycompressing CA<12> on a ×8 4K part, CA<11> on a ×16 4K part, or RA<12>on any 8K part. This address compression combines the data from upperand lower 16 Meg array sections within a 32 Meg array. This test modecan be combined with other test modes.

[0671] 2. CA9COMP—This test mode provides 2× address compression withoutwriting adjacent bits but does cross redundancy regions by compressingCA<9>. This address compression combines the data from upper and lower64 Meg quadrants. This test mode can be combined with other test modes.

[0672] 3. 32MEGCOMP—This test mode provides 2× address compressionwithout writing adjacent bits but does cross redundancy regions bycompressing CA<11> for a ×8 part (CA<10> for a ×16 8K part, CA<12> for a×4 8K part or RA<13> for any 16K part). This address compressioncombines the data from left and right 32 Megs within 64 Meg quadrants.This test mode can be combined with other test modes.

[0673] 4. REDROW—This test mode allows independent testing of the rowredundant elements. The addresses at RAS and CAS during subsequentcycles select the bits to be accessed. From the row pretest, if one ofthe hard-coded addresses used to select a redundant row is entered, thesubsequent column addresses will be from this redundant row. The 32redundant row banks per octant are hard-coded using row addresses RA0-6.For the standard 8K refresh, all 32 MEG octants will fire a redundantrow. For the 8K-×4 part, CA9 and CA12 determine which octant isconnected to the DQs. If both REDROW and REDCOL are selected, the rowaddress selects one of the redundant row elements, while the columnaddress selects either a normal or redundant column. This allows testingof crossing redundant bits. This test mode can be combined withDCSACOMP, CA9COMP, 32MEGCOMP or CAlOCOMP test modes. Also see thedescrition of “redundancy pretest” herein below.

[0674] 5. REDCOL—This test mode allows independent testing of columnredundant elements. The column redundant elements use hard-codedaddresses to enable them. While performing column pretest, the columnaddress is fully decoded which permits testing redundant columns or anynormal columns that don't match the hard-coded addresses. Since the 64redundant column locations are fully decoded it requires all columnaddresses to select them. The redundant element crossing bits are testedif both REDROW and REDCOL are loaded. This test mode can be combinedwith DCSACOMP, CA9COMP, 32MEGCOMP or CA10COMP test modes.

[0675] 6. ALLROW—The RAS cycle following the selection of this test modewill latch all bits on the “seed” wordline selected by the row address.On each of the next 2 WE signal edges another ¼ of the rows within a 2Meg section of each octant will be brought high. On the 3rd WEtransition another quarter of the rows will be brought high and the DVC2generator will be disabled. The 4th WE transition will bring the lastquarter of the rows high and will force DVC2 high. After the 4th WEtransition WE will control the voltage of DVC2. If WE is high then DVC2will be pulled to internal Vcc through a p-channel device; if WE is lowDVC2 will be pulled to GND. See FIG. 104. Once RAS is brought low, thedata stored in the memory cells will be corrupted since EQ will firebefore all wordlines are low. When combining with other test modes, thismust be the last WCBR entered. The ALLROW high test mode is described ingreater detail hereinbelow in conjunction with FIGS. 104, 108, and 109.

[0676] 7. HALFROW—Similar to the ALLROW test mode, HALFROW will Allow AOto control whether EVEN or ODD rows are brought high. All otherfunctions of HALFROW are the same as ALLROW.

[0677] 8. DISLOCK—This test mode disables the RAS and Write lockoutcircuit so that full characterization can be done.

[0678] 9. DISRED—This test mode disables all row and column redundantelements.

[0679] 10. FLOATDVC2—This test mode disables the AVC2 and DVC2generators allowing the voltage on the cellplate and digitlines to beexternally driven.

[0680] 11. FLOATVBB—This test mode will disable the VBB pump and floatthe substrate.

[0681] 12. GNDVBB—This test mode will disable the Vbb pump and groundthe substrate.

[0682] 13. FUSEID—This test mode allows access to 64 bits of laser andantifuse FuseID, 32 bits of data representing currently active testmodes, and 24 bits representing the status of various chip options. Allbits will be accessible through DQ<0>. These bits are accessed using rowaddress <1:4> to select 1 of 16 banks and column address <0:7> to select1 of 8 bits in each bank. Table 8 below lists the us FuseID banks.Currently the first 7 banks of FuseID aser with bank 7 as the onlyantifuse bank. TABLE 8 FUSEID Test mode Addressing Bank Row Addr Col.Addr Test mode 0-6 0-12 0-7 Probe programmable FID (Laser)  7 14 0-7Backend programmable FID (antifuse)  8 16 0 CLEAR 1 DCSACOMP 2 CA9COMP 332MEGCOMP 4 REDROW 5 REDCOL 6 ALLROW 7 HALFROW  9 18 0 DISLOCK 1 DISRED2 FLOATDVC2 3 FLOATVBB 4 GNDVBB 5 FUSEID 6 VCCPCLAMP 7 FAST 10 20 0ANTIFUSE 1 CA10COMP 2 FUSESTRESS 3 PASSVCC 4 REGOFF 5 NOTOPO 6 REGPRE 7OPTPROG 11 22 0-7 SEL32M<0:7> Test mode 12 24 0-7 DVC2 Status<0:7> 13 260-7 32Meg Select<0:7> (antifuse or laser fuse option) 14 28 0 FAST 18KOPT 2 128MEG

[0683]FIG. 105 illustrates the timing for reading out FUSEIDinformation. After the RAS* signal goes low at time 1284, a bank address1285 is latched. Later, the CAS* signal goes low. Each CAS* cycle, whilethe RAS* signal is held low, is used for accessing bits. In theembodiment illustratively shown in FIG. 105, eight bits (B0 to B7) perbank are accessed per read cycle 1286. The WE* signal is held inactivehigh. Bits B0, B1, B2,. . . B7 are latched for access prior to each CAS*cycle. In other words, transition times 1287, 1288, 1289, 1290 of theaddress signal respectively lead transition times 1291, 1292, 1293, 1294of the CAS* signal. Each of bits B0 through B7 may then be provided tothe data path and output.

[0684] Table 9 provides additional details of certain exemplary valueswhich may be represented by banks 0-7. A blown laser fuse in the fuse IDbanks fires the DQ<1> output pin high. This is the case for banks <0:6>of fuse ID. In bank 7 antifuses are used and therefore a “blown” fusewill drive the DQ<1> output pin low. Note that the generic bits willcontain both 8 antifuses and 2 laser fuses. Fuse ID data register fieldswill then be scrambled using standardized fuse ID bit #'s as follows:TABLE 9 FUSEID Specification # of Fuse ID bit #'s Maximum Fuses LSB toMSB Range Used Range EXPLANATION 23   #0-#22 0 to 8388607 0 to 5399999 7digit fuse ID lot number “WWFSSSS” consisting of work week WW (01-53),FAB digit F (1-9), and 4 digit wafer scribe number SSSS, (0000-9999).Will match the lot number on the traveler for non-bonus lots. For bonuslots, and off-line database will have to map wafer scribe numbers to thetraveler lot number.  6 #23-#28 0 to 63 1-50 Wafer number 12 #29-#42 0to 4095 0 to ?? Ordinal die position register that is a function of Xand Y probe coordinates i.e. diepos = F(X, Y). Preferred function is tocode for a rectangular region covering the wafer leading to a functionof the form diepos = (Y + A) * (# of rows) + X + B where A and B areconstants to account for the placement of the origin. A generous amounthas been assigned here to allow distinction between 6 and 8 inch waferpositions for which mutually exclusive die position ranges would beused. This would be handled by 2 different sets of values for the A andB constants. In the event that 4095 combos are insufficient (unlikely tobe the case on any future DRAM or SRAM design), additional bits can betaken from the generic designator register below. 8 antifuse #43-#50 0to 255 0 to 255 Generic designator register for miscellaneous uses. Willbe 2 laser programmed and read as a single register. Possible valueswill be defined as needed over the life of the design. Will be treatedas “used” from the beginning with a default value of 0 even though allpossible values are initially undefined. (This information will includethe fast/slow option code fuse.) Product engineers should be responsiblefor coordinating the usage of these bits.  2 #51-#52 O to 3 0 to 3 Willbe encoded by the function fid_year = year % 4 where “%” is the modulusor remainder function. For 1994, the fid_year value would be 2. Avoidsnon-unique fuse ID's in case lot number and work week rollover.  7#53-#59 0 to 127 0 to 127 Design Revision register. Should be able toopen these fuses with both metal mask and laser. “Hard coding” by themetal mask is the preferred method. Laser programming is used as abackup. Will be reprogrammed whenever the metal mask is taped out. Insome rare cases, a metal mask may be taped out just to reprogram thisregister given there are significant enough changes on other layers torequire careful backend sorting between mask sets.  4 #60-#63 0 to 15 0to 15 Parity error detection bits. This helps determine whether afailing condition on a reject affected a correct fuse ID read. As abonus, it also serves as a fuse blow process monitor. (The errordetection will apply to the entire die id word.)

[0685] See modes 24-31 for the numbering of the arrays which correspondto the DVC2 status and 32 Meg Select Bits. The FUSEID is programmedusing the OPTPROG test mode, which is mode 23 below.

[0686] 14. VCCPCLAMP—This test mode disconnects the clamp between Vccand Vccp allowing the characterization of the Vccp pump. See FIG. 574.This allows the Vccp level to be elevated at low Vcc stressing siliconpits between memory cells.

[0687] 15. FASTTM—This test mode speeds up the EQ, ISO, Row Addresslatch, and P and N Sense Amp enable timing paths.

[0688] 16. ANTIFUSE—This test mode is used to test and program the rowand column redundancy antifuse elements.

[0689] 17. CA10COMP—This test mode provides 2× address compression on ×4and ×8 parts or 2× data compression on ×16 parts without writingadjacent bits but does cross redundancy regions. On a ×4 or ×8 partCA<10> is compressed. This combines left and right 16 Megs within a 32Meg octant. On a ×16 part this is DQ compression. This test mode can becombined with other test modes.

[0690] 18. FUSESTRESS—This test mode applies Vcc across all antifuses.The DVC2E line is pulled to Vccp and the antifuses are all read, whichstresses the antifuses with Vcc. The antifuses will be stressed as longas this test mode is selected and RAS is low.

[0691] 19. PASSVCC—This test mode passes the internal periphery Vcc ontoDQ1.

[0692] 20. REGOFFTM—This test mode will disable the regulator and shortexternal Vccx and internal Vcc.

[0693] 21. NOTOPO—This test mode will disable the topo scramblercircuit.

[0694] 22. REGPRETM—This test mode uses RA<5:9> to pretest the trimvalues on the voltage regulator. The addresses map to the fuses as shownin Table 10 below. A HIGH address value represents a blown fuse. Notethat at least one address needs to be high throughout the RAS low timeof this test mode. A timing diagram illustrating the timing of theREGPRETM test mode is set forth in FIG. 106. TABLE 10 Address to fusemap for REGPRETM Test Mode RA FUSE 5 REF12* 6 REF24* 7 REF48* 8 REF100A*9 REF100B*

[0695] 23. OPTPROG—This test mode enables the antifuse options andantifuse FUSEID bits to be programmed. A <10> is used as the CGND signalwhich sets the programming voltage and either DQ<3> or OE is used asboth the chip select and to set the program duration on the antifuse. OEcan be used in situations where the DQ's may be OR'ed together frommultiple parts and DQ<3> can be used in situations where OE is grounded.A timing diagram illustrating the timing of the OPTPROG test mode is setforth in FIG. 107.

[0696] 24. 32 Meg Pretest<0>—This test mode disables array<0> (38 inFIG. 2) by powering down Vccp, DVC2 and AVC2.

[0697] 25. 32 Meg Pretest<1>—This test mode disables array<1> (40 inFIG. 2) by powering down Vccp, DVC2 and AVC2.

[0698] 26. 32 Meg Pretest<2>—This test mode disables array<2> (31 inFIG. 2) by powering down Vccp, DVC2 and AVC2.

[0699] 27. 32 Meg Pretest<3>—This test mode disables array<3> (33 inFIG. 2) by powering down Vccp, DVC2 and AVC2.

[0700] 28. 32 Meg Pretest<4>—This test mode disables array<4> (27 inFIG. 2) by powering down Vccp, DVC2 and AVC2.

[0701] 29. 32 Meg Pretest<5>—This test mode disables array<5> (25 inFIG. 2) by powering down Vccp, DVC2 and AVC2.

[0702] 30. 32 Meg Pretest<6>—This test mode disables array<6> (47 inFIG. 2) by powering down Vccp, DVC2 and AVC2.

[0703] 31. 32 Meg Pretest <7>—This test mode disables array<7> (45 inFIG. 2) by powering down Vccp, DVC2 and AVC2.

[0704] All laser/antifuse options can be read out through the FUSEIDtest mode on banks 13 and 14.

[0705] FAST—Removes delay in the raend_enph and wl_tracking circuits.

[0706] 128 MEG—Forces the part to be accessed as a 128 Meg density part.This option must be combined with 4 of the SEL32MOPT<0:7> option.

[0707] 8KOPT—Puts the part in 4K refresh mode if combined with 128 MEGoption, otherwise the part will be in 16K refresh.

[0708] SEL32MOPT<0:7>—Blowing the fuse on these options disables thecorresponding 32 Meg array.

[0709] The following laser options are available in the presentpreferred embodiment:

[0710] DISREG—Disables the regulator by clamping Vccx to Vcc through alarge p-channel.

[0711] DISANTIFUSE—Disables the backend redundancy antifuses. AntifuseFID bits are still available.

[0712] REF12*—LSB of voltage regulator trim.

[0713] REF24*—regulator trim.

[0714] REF48*—regulator trim.

[0715] REF100A*—regulator trim.

[0716] REF100B*—MSB of voltage regulator trim.

[0717] Referring now to the ALLROW high test mode, as noted that testmode is used to rapidly reproduce data for testing a memory array. Inthe preferred embodiment, the test mode operates on 2 Meg “array slices”1400 taken from a 32 Meg array block 31, as illustrated in FIG. 108.Each array slice 1400 includes eight adjacent 256 k arrays 50 in the 32Meg array block 31. The 32 Meg array block 31 is discussed in moredetail hereinabove in Section III.

[0718]FIG. 109 illustrates the details of a 256 k array 50 making up aportion of the array slice 1400, and also shows sense amps 60, 62located above and below the 256 k array 50 and row decoders 56, 58located on the left and right of the 256 k array 50, respectively. The256 k array 50, the sense amps 60, 62, and the row decoders 56, 58 aredescribed in more detail hereinabove in Section III. A “seed row” 1402,consisting of a number of storage nodes or storage elements includingboth true and complement data, extends across the 256 k array 50 andacross the array slice 1400 (as shown in FIG. 108), and is programmedwith a pattern of data that is used to test the array. Patterns of dataused to test for defects in memory arrays are well known in the art ofsemiconductor fabrication and they will not be discussed herein. Thewriting of data into the 256 k array is a relatively slow processbecause in most memory devices no more than one or two bits of data canbe written in the array slice 1400 during each write cycle. Once theseed row 1402 is written, however, the present invention allows the datastored in the seed row 1402 to be quickly duplicated into the remainingrows within the array slice 1400. More specifically, by “firing” theappropriate wordline, the data stored in the seed row 1402 is placed onthe digitlines 68, 68′, 69, 69′ in the 256 k array 50. Once the data ison the digitlines 68, 68′, 69, 69′, the data is latched by the senseamps 60, 62. Thereafter, the latched data may be stored in any row ofstorage nodes 5 in the 256 k array 50 by firing the appropriate wordlineto connect the row of storage nodes to the digitlines 68, 68′, 69, 69′.

[0719] In the preferred embodiment, the seed row 1402 is written in aconventional manner. In addition, the seed row 1402 is always the samerow within the 256 k array 50 so that the test mode knows where to findthe data. After the seed row 1400 is written, the test mode is enteredby any one of many means known in the art. Once in the test mode,signals take on special meanings to accomplish the testing. Cycling theRAS* signal will cause all storage nodes 5 in the seed row 1402 to beconnected to the digitlines 68, 68′, 69, 69′, so that the sense amps 60,62 latch the data. After the data is latched, cycling the CAS signalwill cause additional rows of storage nodes 5 to be connected to thedigitlines 68, 68′, 69, 69′ and, thereby, to have the data on thedigitlines 68, 68′, 69, 69′ written thereto. Preferably, multiple rowsare accessed with each CAS cycle so that the array 50 is written morequickly. In the preferred embodiment, each CAS cycle causesapproximately 25% of the rows in the array slice 1400 to be programmedwith the data on the digitlines 68, 68′, 69, 69′. As a result, only fourCAS cycles are required to program an entire array slice 1400 from asingle seed row 1402. The choice of duplicating the array slice 1400 in25% increments is based on considerations such as power supply capacity.Greater or smaller increments may, of course, be used. For example, insome applications the entire array slice 1400 may be programmed in asingle CAS cycle. Furthermore, external signals other than CAS and RAS*may be used to control the test mode.

[0720] In the present invention, the row and column address signalsrequired to select the array slice 1400 are provided externally. Incontrast, the row address signals required to select rows within thearray slice 1400 are provided internally by the test mode. The test modeselects 25% of the array slice 1400 by generating a high logic statesignal for each predecoded row address signal RA_(—)0<0:1>, RA34<0:3>,RA56<0:3>, and RA78<0:3>, in combination with generating a high logicstate signal for only one of the four predecoded row address signalsRA12<0:3>. The one row address signal RA12<n> that is a high logic statewill determine which 25% of the array slice 1400 is selected. The rowaddress mapping and column address mapping schemes for the presentinvention are discussed in more detail hereinabove in Section V. Rowaddress data signals RA12<0:3> are provided by a CAS before RAS CBRripple counter formed from cascading one bit CBR counters located in therow address buffers. In normal operation, the CBR ripple counter is usedto provide internally-generated refresh address signals, but in the allrow high test mode it is used to automatically generate row addresssignals RA12<0:3> for each CAS cycle. During each CAS cycle, the CBRripple counter generates new row address signals RA12<0:3>. For example,during the first CAS cycle, the CBR ripple counter will generate a highlogic state signal for row address signal RA12<0> only, therebyselecting 25% of the array slice 1400. During the second CAS cycle, theCBR ripple counter will generate a high logic state signal for rowaddress signal RA12<1> only, thereby selecting a different 25 k of thearray slice 1400. Likewise, during third and fourth CAS cycles the CBRcounter will generate high logic state signals for only row addresssignals RA12<2> and RA12<3>, respectively. After four CAS cycles, theCBR counter will have selected the entire array slice 1400.

[0721] Referring back to FIG. 104, FIG. 104 illustrates timing diagramsof the RAS*, CAS, and WE signals used to practice the present invention.As shown, RAS* goes to a low logic state at a time indicated byreference number 1410 to fire the seed row 1402 so that the seed rowdata is latched by the sense amps 60, 62. A delay period 1412 followingthe RAS* cycle allows the sense amps 60, 62 to reach a stable state. Ata time indicated by reference number 1414, WE goes to a low logic stateand 25% of the rows in the array slice 1400, represented by row addresssignal RA12<0>, are written with the data latched by the sense amps 60,62. On the rising edge 1416 of the WE signal, another 25% of the rows inthe array slice, represented by row address signal RA12<1>, is written.At trailing edge 1418 of the WE signal, another 25% of the rows in thearray slice, represented by row address signal RA12<2>, is written. DVC2is also disabled. At rising edge 1420, the final 25% of the rows in thearray slice, represented by row address signal RA12<3>, is written. Onthe following trailing edge, DVC2 is set low. After the array slice 1400has been written, the data can be read and analyzed to identify defectsin the DRAM. Testing may also proceed to other array slices 1400 withinthe DRAM so that, with multiple iterations, the entire DRAM may betested for defects.

[0722] One advantage of the all row high test mode is that it allowsdata to be quickly reproduced in a memory array. Another advantage isthat the rate at which data is reproduced can be controlled bycontrolling the RAS*, CAS, and WE signals. As a result, the test modecan be used to study how quickly and in what manner a memory device willreact during testing to better understand the DRAM 10 and to optimizethe testing process.

[0723] In addition to operating in a plurality of test modes, in thepresent preferred embodiment, redundancy pretesting can be performed.There are two possible ways to use the redundancy pretest. At Probethere is the REDPRE probe pad. This pad is latched at RAS and CAS timeto function as another address. If REDPRE is high at RAS time then theaccompanying address will function as a redundancy pretest address. Thesame is true at CAS time. If the REDPRE pad is low at RAS time theaddress pins function in their normal manner. The same is true again atCAS time. That allows Probe to enter a redundancy pretest address at Rowtime and follow that with a normal column address. Also, a normal Rowaddress can be followed by a redundant pretest column address. Once thepart is packaged the REDPRE pad is no longer available and the REDROWand REDCOL test modes must be used.

[0724] The row redundancy pretest addresses are described in tables 11,12 and 13. There are 32 elements in each 32 Meg octant organized into 8banks of 4 elements. Element 3 in each bank is laser or antifuseprogrammable. Two physical rows are replaced in a 32 Meg array by eachelement. To exercise both physical rows attached to any particularelement both states of the 16MEG* signal must be used. Table 11illustrates how 16 MEG is controlled by the various part types.Redundant rows can be pretested even if some of the redundancy has beenenabled or if all redundancy has been disabled. TABLE 11 16 MEG signalcontrol part type 16 MEG X8 4K CA12 X16 4K CA11 ANY 8K RA<12> ANY 16KRA<12>

[0725] TABLE 12 Row Element Address Within a Bank RA0 RA12 Element 0 0 01 1 1 0 2 2 1 3 3 laser/elect

[0726] TABLE 13 Row Pretest Bank Address RA34 RA56 Bank 0 0 0 1 0 1 2 02 3 0 3 0 1 4 1 1 5 2 1 6 3 1 7

[0727] Tables 14 to 19 below show the pretest addressing for theredundant column elements and their corresponding DQ. Each octantcontains 32 column elements grouped into 8 banks of 4 elements. Element3 is both laser or antifuse programmable. Table 14 shows how CA9, 32MEGare used to decode the octants. Addresses CA11, CA10 and CA7 are used todecode the various banks and CA1 and CA0 are used to decode 1 of 4elements within each bank. Address CA8 selects between I/O pairs andmust be tested in both states. Because the column pretest addresses feedthrough the laser fuses, the pretest may not work if any redundantelements have been enabled. Redundant column elements cannot bepretested if redundancy has been disabled. TABLE 14 Addressing forColumn Redundancy Pretest 32 MEG<0> 32 MEG<1> 32 MEG <0 > 32 MEG<1>CA9<1> Octant Octant Octant Octant 7 6 5 4 Periph CA9<0> Octant OctantOctant Octant 0 1 2 3

[0728] TABLE 15 32 MEG Signal Control Part Type 32 MEG ANY 16K RA<13> X48K or 4K CA<12> X8 8K or 4K CA<11> X16 8K or 4K CA<10>

[0729] TABLE 16 Column Element Address Within a Bank CA01 Element 0 0 11 2 2 3 3 Laser/Elect

[0730] TABLE 17 Column Pretest Bank Addresses (X4) CA1011 CA7 Bank 0 0 00 1 1 1 0 2 1 1 3 2 0 4 2 1 5 3 0 6 3 1 7

[0731] TABLE 18 Column Pretest Bank Addresses (X8) CA10 CA7 Banks 0 00,4 0 1 1,5 1 0 2,6 1 1 3,7

[0732] TABLE 19 Column Pretest Addresses (X16) CA7 Banks 0 0,2,4,6 11,3,5,7

[0733]FIG. 110 illustrates the chip 10 of the present invention andprovides some exemplary dimensions of one embodiment. In the illustratedembodiment, total die space is approximately 574.5 k mils² withapproximately 323.5 k mils² devoted to the active array. Thus, theactive array occupies over half the total die space.

[0734]FIG. 111 illustrates an example of the connection of the bondingpads of the present invention to a lead frame 1422. As can be seen inFIG. 111, there are tie bars 1424 connecting several lead fingers 1425to the lead frame 1422, thereby supporting the lead fingers 1425 so theydo not move during a molding process. There are also combination tiebars and bus bars 1426. The combination tie bar and bus bar 1426supports lead fingers 1425 during the molding process and, after the tiebars are cut in a trim and form process, the bus bar remains to serve asa power bus or a ground bus. The chip 10 of the present invention may beencapsulated in a package during a molding process, so that the packagehas an encapsulating body and electrically conductive interconnect pins,or leads, extending outwardly from the body. After the molding process,the trim and form process separates the lead frame from the leads andseparates the leads from each other.

[0735]FIG. 112 illustrates a substrate carrying a plurality of chips 10,each constructed according to the teachings of the present invention.The size of the substrate, or wafer, is determined by the size of thefabrication equipment. A six inch wafer size is typical.

[0736]FIG. 113 is a block diagram illustrating the DRAM 10 of thepresent invention used in a microprocessor-based system 1430. The DRAM10 is under the control of a microprocessor 1432 which may be programmedto carry out particular functions as is known in the art. Themicroprocessor-based system 1430 may be used, for example, in a personalcomputer, computer workstations, and consumer electronics products.

[0737] XII. Conclusion While the present invention has been described inconjunction with preferred embodiments thereof, many modifications andvariations will be apparent to those of ordinary skill in the art. Forexample, the number of individual arrays and their organization intoarray blocks, and the organization of the array blocks into quadrantsmay be varied. Rotation of an array by ninety degrees causes the rows tobecome columns and the columns to become rows. Therefore, descriptorssuch as “between adjacent columns” should be understood as including“between adjacent rows” in such a rotated device. Additionally, theposition of the peripheral devices may be interchanged such that devicesin the “columns” are in the “rows” and vice versa. The amount andlocation of the decoupling capacitors may be varied. More or lessredundancy may be provided, and various combinations of laser andelectrical types of fuses may be provided for logically replacingdefective rows/columns with operational rows/columns. Other types oftest modes may be supported. The number and location of the voltagesupplies may be varied and numerous other types of circuits and logicmay be supplied to provide the described functionality.

[0738] Other modifications and variations include varying theorientation of the array with respect to the periphery. The sequence ofpowering up the power supplies may be varied. Various signals may becombined with switched gates to effect different or additionalfunctionality. Address space and DQ plans can be allocated differently.The distribution of address and control signals, predecoded versusnonpredecoded, results in various structural differences which areapparent to those of ordinary skill in the art. Decisions such as thenumber of metal layers also leads to distinctive circuit implementation.For example, the use of only two metal layers mandates the use of localrow decoders. Different overall dimensions may be employed, as well asdifferent bonding schemes between the chip and the lead frame.

[0739] Other decisions such as the size of the overall chip, density,memory size, and process limitations, will lead to many modificationsand variations of the present invention too numerous to enumerate. Theforegoing description and the following claims are intended to cover allsuch modifications and variations.

What is claimed is:
 1. A memory, comprising: a plurality of memory cellsproviding at least 256 meg of storage; a plurality of peripheral devicesfor writing information into and reading information out of saidplurality of memory cells; a power supply; a plurality of pads; and notmore than two layers of metal conductors providing interconnectionbetween said plurality of memory cells, said plurality of peripheraldevices, said power supply, and said plurality of pads.
 2. The memory ofclaim 1 wherein said memory is fabricated on a die approximately 24.7 mmby 15 mm.
 3. The memory of claim 1 wherein said plurality of memorycells is arranged into a plurality of individual arrays, said individualarrays being organized into rows and columns to form a plurality ofarray blocks.
 4. The memory of claim 3 wherein said plurality ofperipheral devices includes a plurality of sense amplifiers positionedbetween adjacent rows of individual arrays and a plurality of rowdecoders positioned between adjacent columns of individual arrays. 5.The memory of claim 4 additionally comprising digitlines extendingthrough each of said plurality of individual arrays and into said senseamplifiers, and I/O lines running between adjacent rows of individualarrays and through said sense amplifiers, said sense amplifiersincluding circuits for transferring signals on said digitlines to saidI/O lines.
 6. The memory of claim 5 additionally comprising datalinesrunning between adjacent columns of individual arrays and through saidrow decoders to form intersections with said I/O lines, said pluralityof peripheral devices including a plurality of multiplexors positionedat certain of said intersections of said I/O lines and said datalinesfor transferring signals on said I/O lines to said datalines.
 7. Thememory of claim 6 wherein said plurality of array blocks is organizedinto a plurality of array quadrants, and wherein said plurality ofperipheral devices includes an array I/O block for servicing each ofsaid array quadrants, a plurality of data read multiplexers responsiveto said array I/O blocks, a plurality of data output buffers responsiveto said plurality of data read multiplexers, and a plurality of data paddrivers responsive to said plurality of data output buffers for makingthe read data available at said plurality of pads.
 8. The memory ofclaim 7 wherein said plurality of peripheral devices includes aplurality of data in buffers response to data available at saidplurality of pads and a plurality of data write multiplexors responsiveto said plurality of data in buffers and wherein said array I/O blocksare responsive to said plurality of data write multiplexors.
 9. Thememory of claim 8 additionally comprising a data test path circuitinterposed between said array I/O blocks and said plurality of data readmultiplexers.
 10. The memory of claim 9 wherein said individual arraysof memory cells include memory cells arranged in rows and columns, saidmemory additionally comprising logic for cycling through sets of rows ofcells in response to an all row high test request.
 11. The memory ofclaim 3 wherein said metal conductors form a web around each array blockand a grid within each array block.
 12. The memory of claim 3additionally comprising switches for disconnecting each of saidplurality of array blocks from said power supply.
 13. The memory ofclaim 12 wherein said power supply has a modular design such thatcertain modules can be shut down in response to the number of arrayblocks connected to said power supply.
 14. The memory of claim 1 whereinsaid power supply has a modular design such that certain modules can beshut down in response to a refresh mode of operation.
 15. The memory ofclaim 1 wherein said pads are centrally located.
 16. The memory of claim15 wherein said power supply is positioned proximate to said pads. 17.The memory of claim 1 wherein said power supply includes a voltageregulator for producing an array voltage, voltage pumps for producingboosted voltages, and a voltage generator for producing a bias voltagefor use by said random access memory.
 18. The memory of claim 17additionally comprising a sequence circuit for controlling the sequencein which said voltage regulator, voltage pumps, and voltage generatorare powered up.
 19. A memory fabricated on a die, comprising: aplurality of memory cells providing at least 256 meg of storage; aplurality of peripheral devices for writing information into and readinginformation out of said plurality of memory cells; a power supply; aplurality of pads; and layers of metal conductors for providinginterconnections between said plurality of memory cells, said pluralityof peripheral devices, said power supply, and said plurality of pads,and wherein the die is approximately 24.7 mm by 15 mm.
 20. The memory ofclaim 1 wherein said layers of metal do not exceed two.
 21. The memoryof claim 19 wherein said plurality of memory cells is arranged into aplurality of individual arrays, said individual arrays being organizedinto rows and columns to form a plurality of array blocks.
 22. Thememory of claim 21 wherein said plurality of peripheral devices includesa plurality of sense amplifiers positioned between adjacent rows ofindividual arrays and a plurality of row decoders positioned betweenadjacent columns of individual arrays.
 23. The memory of claim 23additionally comprising digitlines extending through each of saidplurality of individual arrays and into said sense amplifiers, and I/Olines running between adjacent rows of individual arrays and throughsaid sense amplifiers, said sense amplifiers including circuits fortransferring signals on said digitlines to said I/O lines.
 24. Thememory of claim 23 additionally comprising datalines running betweenadjacent columns of individual arrays and through said row decoders toform intersections with said I/O lines, said plurality of peripheraldevices including a plurality of multiplexors, positioned at certain ofsaid intersections of said I/O lines and said datalines for transferringsignals on said I/O lines to said datalines.
 25. The memory of claim 24wherein said plurality of array blocks is organized into a plurality ofarray quadrants, and wherein said plurality of peripheral devicesincludes an array I/O block for servicing each of said array quadrants,a plurality of data read multiplexers responsive to said array I/Oblocks, a plurality of data output buffers responsive to said pluralityof data read multiplexers, and a plurality of data pad driversresponsive to said plurality of data output buffers for making the readdata available at said plurality of pads.
 26. The memory of claim 25wherein said plurality of peripheral devices includes a plurality ofdata in buffers response to data available at said plurality of pads anda plurality of data write multiplexers responsive to said plurality ofdata in buffers and wherein said array I/O blocks are responsive to saidplurality of data write multiplexers.
 27. The memory of claim 26additionally comprising a data test path circuit interposed between saidarray I/O blocks and said plurality of data read multiplexers.
 28. Thememory of claim 27 wherein said individual arrays of memory cellsinclude memory cells arranged in rows and columns, said memoryadditionally comprising logic for cycling through sets of rows of cellsin response to an all row high test request.
 29. The memory of claim 21wherein said metal conductors form a web around each array block and agrid within each array block.
 30. The memory of claim 21 additionallycomprising switches for disconnecting each of said plurality of arrayblocks from said power supply.
 31. The memory of claim 30 wherein saidpower supply has a modular design such that certain modules can be shutdown in response to the number of array blocks connected to said powersupply.
 32. The memory such that of claim 19 wherein said power supplyhas a modular design such that certain modules can be shut down inresponse to a refresh mode of operation.
 33. The memory of claim 19wherein said pads are centrally located.
 34. The memory of claim 33wherein said power supply is positioned proximate to said pads.
 35. Thememory of claim 19 wherein said power supply includes a voltageregulator for producing an array voltage, voltage pumps for producingboosted voltages, and a voltage generator for producing a bias voltagefor use by said random access memory.
 36. The memory of claim 35additionally comprising a sequence circuit for controlling the sequencein which said voltage regulator, voltage pumps, and voltage generatorare powered up.
 37. A memory, comprising: a plurality of memory cellsproviding at least 256 meg of storage, said memory calls beingfabricated at a density of 791,350 bits per square mil; a plurality ofperipheral devices for writing information into and reading informationout of said plurality of memory cells; a power supply; a plurality ofpads; and layers of metal conductors for providing interconnectionsbetween said plurality of memory cells, said plurality of peripheraldevices, said power supply, and said plurality of pads.
 38. The memoryof claim 37 wherein said layers of metal do not exceed two.
 39. Thememory of claim 37 wherein said memory is fabricated on a dieapproximately 24.7 mm by 15 mm.
 40. The memory of claim 37 wherein saidplurality of memory cells is arranged into a plurality of individualarrays, said individual arrays being organized into rows and columns toform a plurality of array blocks.
 41. The memory of claim 40 whereinsaid plurality of peripheral devices includes a plurality of senseamplifiers positioned between adjacent rows of individual arrays and aplurality of row decoders positioned between adjacent columns ofindividual arrays.
 42. The memory of claim 41 additionally comprisingdigitlines extending through each of said plurality of individual arraysand into said sense amplifiers, and I/O lines running between adjacentrows of individual arrays and through said sense amplifiers, said senseamplifiers including circuits for transferring signals on saiddigitlines to said I/O lines.
 43. The memory of claim 42 additionallycomprising datalines running between adjacent columns of individualarrays and through said row decoders to form intersections with said I/Olines, said plurality of peripheral devices including a plurality ofmultiplexers, positioned at certain of said intersections of said I/Olines and said data lines for transferring signals on said lines to saiddata lines.
 44. The memory of claim 43 wherein said plurality of arrayblocks is organized into a plurality of array quadrants, and whereinsaid plurality of peripheral devices includes an array I/O block forservicing each of said array quadrants, a plurality of data readmultiplexers responsive to said array I/O blocks, a plurality of dataoutput buffers responsive to said plurality of data read multiplexers,and a plurality of data pad drivers responsive to said plurality of dataoutput buffers for making the read data available at said plurality ofpads.
 45. The memory of claim 44 wherein said plurality of peripheraldevices includes a plurality of data in buffers response to dataavailable at said plurality of pads and a plurality of data writemultiplexers responsive to said plurality of data in buffers and whereinsaid array I/O blocks are responsive to said plurality of data writemultiplexers.
 46. The memory of claim 45 additionally comprising a datatest path circuit interposed between said array I/O blocks and saidplurality of data read multiplexers.
 47. The dynamic random accessmemory of claim 46 wherein said individual arrays of memory cellsinclude memory cells arranged in rows and columns, said memoryadditionally comprising logic for cycling through sets of rows of cellsin response to an all row high test request.
 48. The memory of claim 40wherein said metal conductors form a web around each array block and agrid within each array block.
 49. The memory of claim 40 additionallycomprising switches for disconnecting each of said plurality of arrayblocks from said power supply.
 50. The memory of claim 49 wherein saidpower supply has a modular design such that certain modules can be shutdown in response to the number of array blocks connected to said powersupply.
 51. The memory of claim 37 wherein said power supply has amodular design such that certain modules can be shut down in response toa refresh mode of operation.
 52. The memory of claim 37 wherein saidpads are centrally located.
 53. The memory of claim 52 wherein saidpower supply is positioned proximate to said pads.
 54. The memory ofclaim 37 wherein said power supply includes a voltage regulator forproducing an array voltage, voltage pumps for producing boostedvoltages, and a voltage generator for producing a bias voltage for useby said random access memory.
 55. The memory of claim 54 additionallycomprising a sequence circuit for controlling the sequence in which saidvoltage regulator, voltage pumps, and voltage generator are powered up.56. A die carrying a 256 meg memory device, said die having not morethan two layers of metal conductors.
 57. A dynamic random access memory,comprising: a plurality of individual arrays of memory cells, saidindividual arrays organized into rows and columns to form a plurality ofarray blocks; a plurality of pads located centrally with respect to saidarray blocks; a plurality of peripheral devices for transferring databetween said memory cells and said plurality of pads; a plurality ofvoltage supplies located proximate said plurality of pads for generatinga plurality of supply voltages; and a power distribution bus fordelivering said plurality of supply voltages to said individual arraysand said plurality of peripheral devices.
 58. A power distribution busfor a memory device constructed of memory blocks organized into anarray, said bus comprised of a first plurality of conductors forcarrying the voltages used by the array and forming a web surroundingeach of the blocks of the array, and a second plurality of conductorsextending from said web into each of the memory blocks to form a gridwithin each of the memory blocks.
 59. A dynamic random access memory,comprising: an array of memory cells; a plurality of peripheral devicesfor writing data into said memory cells and for reading data out of saidmemory cells; a plurality of voltage supplies for generating a pluralityof supply voltages, at least one of said voltage supplies being avoltage regulator comprised of a plurality of power amplifiers andwherein said power amplifiers are organized into a plurality of groupsoperable in one of separate and concurrent operating modes to achievepredetermined levels of output power; and a power distribution bus fordelivering said plurality of supply voltages to said array and saidplurality of peripheral devices.
 60. A voltage regulator for a dynamicrandom access memory, said voltage regulator comprising: a voltagereference circuit for producing a reference voltage; a plurality ofpower amplifiers for developing a supply voltage for supplying power tothe dynamic random access memory, said power amplifiers being responsiveto said reference voltage and having a gain greater than one; and acontrol circuit for producing control signals for controlling saidplurality of power amplifiers.
 61. A dynamic random access memory,comprising: an array of memory cells configured in separatelycontrollable array blocks; a plurality of peripheral devices responsiveto external signals for writing data into said array blocks and forreading data out of said array blocks; a plurality of voltage suppliesfor generating a plurality of supply voltages, at least one of saidvoltage supplies being a voltage regulator comprised of a plurality ofpower amplifiers and at least one of said power amplifiers beingassociated with each of said array blocks; a plurality of powerdistribution switches; and a power distribution bus for delivering saidplurality of supply voltages to said array blocks through said pluralityof switches and to said plurality of peripheral devices, and whereinsaid plurality of peripheral devices includes logic for controlling eachof said plurality of switches and for controlling the state of each ofsaid power amplifiers.
 62. A voltage regulator for a dynamic randomaccess memory having an array divided into array blocks, said voltageregulator comprising: a voltage reference circuit for producing areference voltage; multiple power amplifiers for developing a supplyvoltage, said power amplifiers arranged such that certain of said poweramplifiers supply power to certain of the array blocks; and controlcircuitry for disabling a power amplifier when the array blockassociated therewith is disabled.
 63. A power supply for a dynamicrandom access memory having a plurality of array blocks and a pluralityof pads located centrally of the array blocks, said power supplycomprising: a plurality of voltage supplies located proximate to theplurality of pads for producing supply voltages for the plurality ofarray blocks.
 64. A dynamic random access memory, comprising: an arrayof memory cells; a plurality of peripheral devices for writing data intosaid memory cells and for reading data out of said memory cells; aplurality of voltage supplies for generating a plurality of supplyvoltages, at least one of said voltage supplies being a voltage pumpcomprised of a plurality of voltage pump circuits and wherein saidvoltage pump circuits are organized into a plurality of groups operablein one of separate and concurrent operating modes to achievepredetermined levels of output power; and a power distribution bus fordelivering said plurality of supply voltages to said array and saidplurality of peripheral devices.
 65. A voltage pump for an integratedcircuit, comprising: a plurality of voltage pump circuits operable inresponse to a clock signal input thereto, said plurality of voltage pumpcircuits being divided into a plurality of groups for operation inresponse to an enable signal produced by the integrated circuit in oneof separate or concurrent operating modes to achieve predeterminedlevels of power output; an oscillator circuit for producing said clocksignal; and a regulator circuit for producing first signals forcontrolling said oscillator circuit.
 66. A dynamic random access memory,comprising: an array of memory cells; a plurality of peripheral devicesfor writing data into said memory cells and for reading data out of saidmemory cells; a plurality of voltage supplies responsive to an externalvoltage for generating a plurality of supply voltages for use by saidarray and said plurality of peripheral devices, one of said plurality ofvoltage supplies including a voltage generator producing an outputvoltage; a voltage detection circuit responsive to said output voltagefor producing an overvoltage signal and an undervoltage signalindicative of whether the output voltage is within a first predeterminedrange; and a logic circuit responsive to said overvoltage and saidundervoltage signals for providing an indication of the stability of thevoltage generator.
 67. A stability sensor for a voltage generator whichutilizes pullup and pulldown currents for regulation purposes, saidsensor comprising: a current source responsive to one of the pullup andpulldown currents for producing a source current indicative of thecurrent; a resistor for generating a voltage in response to the sourcecurrent; and an overcurrent circuit responsive to said voltage forproducing a signal indicative of an excessive amount of one of thepullup and pulldown current.
 68. A dynamic random access memory,comprising: an array of memory cells; a plurality of peripheral devicesfor writing data into said memory cells and for reading data out of saidmemory cells; a plurality of voltage supplies responsive to an externalvoltage for generating a plurality of supply voltages for use by saidarray and said plurality of peripheral devices; and a powerup sequencecircuit for controlling the powering up of certain of the plurality ofvoltage supplies in response to the condition of previously powered upvoltage supplies.
 69. A powerup circuit for an integrated circuit havinga voltage supply responsive to a voltage external to the integratedcircuit and generating a feedback signal, said powerup circuitcomprising: a first circuit portion responsive to the external voltagefor producing a first output signal indicative of whether the externalvoltage is above a predetermined value; and a second circuit portionresponsive to said first output signal and the feedback signal forproducing a first enable signal to enable the voltage supply.
 70. Adynamic random access memory, comprising: an array of memory cells, eachcomprised of two storage elements; a plurality of peripheral devices forwriting data into said memory cells and for reading data out of saidmemory cells; a plurality of voltage supplies responsive to an externalvoltage for generating a plurality of supply voltages for use by saidarray and said plurality of peripheral devices; and test mode logic fordetermining whether the memory is in a test mode, and wherein saidplurality of peripheral devices includes a latch circuit responsive to afirst external signal when the memory is in the test mode, for latchingdata stored in a first group of memory elements, and a write enablecircuit responsive to a second external signal when said memory is inthe test mode, for enabling the latched data to be written to a secondgroup of memory elements.
 71. A method of testing a plurality of memoryelements organized in a plurality of rows, comprising the steps of:writing test data into a first row of memory elements; latching the testdata from the first row of memory elements in response to a firstexternal signal; writing the latched test data into a first group ofmemory elements in response to a second external signal; reading thetest data from the second group of memory elements; and comparing thetest data read from the second group of memory elements with the testdata written to the first row of memory elements.
 72. A dynamic randomaccess memory, comprising: a plurality of individual arrays of memorycells, said individual arrays organized into rows and columns to form aplurality of array blocks; a plurality of peripheral devices for writinginformation into said memory cells and for reading information out ofsaid memory cells, said plurality of peripheral devices including aplurality of sense amplifiers positioned between adjacent rows ofindividual arrays in said array blocks and a plurality of row decoderspositioned between adjacent columns of individual arrays in said arrayblocks; and a plurality of voltage supplies for generating a pluralityof supply voltages for use by said array blocks and said plurality ofperipheral devices, and wherein said plurality of individual arraysincludes digitlines extending therethrough and into said senseamplifiers, and wherein said array blocks include I/O lines runningbetween adjacent rows of individual arrays and through said senseamplifiers, said sense amplifiers including circuits for transferringsignals on said digitlines to said I/O lines, and wherein said arrayblocks include datalines running between adjacent columns of individualarrays and through said row decoders to form intersections with said I/Olines, said plurality of peripheral devices including a plurality ofmultiplexers positioned at certain of said intersections of I/O linesand datalines for transferring signals on said I/O lines to saiddatalines.
 73. A data path for a dynamic random access memory having aplurality of data cells organized into rows and columns to form aplurality of individual arrays, the plurality of individual arraysorganized into rows and columns to form a plurality of array blocks,with the array blocks organized into a plurality of quadrants, said datapath comprising: a plurality of sense amplifiers positioned betweenadjacent rows of individual arrays; a plurality of digitlines extendingthrough each individual array and into said sense amplifiers; aplurality of I/O lines running between adjacent rows of individualarrays and through said sense amplifiers, said sense amplifiersincluding circuits for transferring signals on said digitlines to saidI/O lines; a plurality of datalines running between adjacent columns ofindividual arrays to form intersections with said I/O lines; a pluralityof multiplexers positioned at certain of said intersections of I/O linesand datalines for transferring signals on said I/O lines to saiddatalines; a plurality of I/O blocks each responsive to said datalinesfrom one of said plurality of array quadrants; a plurality of data readmultiplexers responsive to said array I/O blocks; a plurality of dataoutput buffers responsive to said plurality data read multiplexers; aplurality of data pad drivers responsive to said plurality of dataoutput buffers for making data read from the cells available at aplurality of pads; a plurality of data in buffers responsive to dataavailable at the plurality of pads; and a plurality of data writemultiplexers responsive to said plurality of data in buffers, andwherein said array I/O blocks are responsive to said plurality of datawrite multiplexers.
 74. An output buffer, comprising: a plurality ofoutput drive transistors connected in series between a first voltagesupply and ground; an output terminal responsive to said seriesconnected transistors; a latch for receiving data to be output to saidoutput terminal; a logic circuit responsive to said latch forcontrolling said output drive transistors to drive a voltage at saidoutput terminal to one of a high and low potential representing a logicstate of the data to be output; a boot capacitor for supplyingadditional voltage to certain of said drive transistors; a holdingtransistor responsive to said logic circuit for connecting said bootcapacitor to a second supply voltage; and a self-timed circuit pathconnected across said holding transistor and said boot capacitor.
 75. Adynamic random access memory, comprising: an array of memory cells; aplurality of peripheral devices for writing data into and reading dataout of said array of memory cells, said peripheral devices including aplurality of programmable multiplexer cells; a power supply; a pluralityof pads; and layers of conductors providing interconnections betweensaid plurality of memory cells, said plurality of peripheral devices,said power supply, and said plurality of pads.
 76. A programmablemultiplexer cell for use in a memory device, comprising: a plurality ofinput lines; a plurality of output lines; a plurality of programmableswitches connecting said plurality of input lines to said plurality ofoutput lines through said multiplexer.
 77. A dynamic random accessmemory, comprising: a plurality of individual arrays of memory cells,said individual arrays having digitlines extending therethrough, saidindividual arrays organized into rows and columns to form a plurality ofarray blocks; a plurality of peripheral devices for writing data intoand for reading data out of said memory cells with said digitlines; apower supply for generating a plurality of supply voltages, said powersupply voltages including a plurality of generators for producing a biasvoltage for biasing said digitlines, said number of generators beingequal to said number of array blocks; and a power distribution bus fordelivering said plurality of supply voltages to said plurality of arrayblocks and said peripheral devices.
 78. A dynamic random access memory,comprising: a plurality of individual arrays of memory cells, saidindividual arrays having digitlines extending therethrough; a pluralityof peripheral devices for writing data into and for reading data out ofsaid memory cells with said digitlines, said peripheral devicesincluding a plurality of sense amplifiers for sensing the signals onsaid digitlines, said sense amplifiers being controlled by controlsignals having a greater magnitude than the magnitude of the datasignals to be written to said memory cells; a power supply forgenerating a plurality of supply voltages; and a power distribution busfor delivering said plurality of supply voltages to said individualarrays and said peripheral devices.
 79. A sense amplifier, comprising: adigitline for connecting an array to I/O lines; an equalization switchadjacent the array for equilibrating said digitline; an n-senseamplifier connected across said digitline; a p-sense amplifier connectedacross said digitline; an isolation switch connected between saidn-sense and said p-sense amplifier and said equalization switch forisolating said n-sense and p-sense amplifier from the array; and aconnection switch for connecting said digitline to the I/O line.
 80. Adynamic random access memory, comprising: a plurality of individualarrays of memory cells, said individual arrays organized into rows andcolumns to form a plurality of array blocks; a plurality of peripheraldevices for writing information into and reading information out of saidplurality of memory cells, said plurality of peripheral devicesincluding a plurality of sense amplifiers; logic for producing aredundant signal for controlling said plurality of peripheral devices; apower supply; a plurality of pads; and not more than a first layer and asecond layer of metal conductors providing interconnections between saidplurality of memory cells, said plurality of peripheral devices, saidlogic, said power supply, and said plurality of pads, said redundantsignal being routed through said sense amplifiers in said second layerof metal.